Utilities
alias
create, list, and delete command aliases
Print list of current aliases
alias alias bc='bc -q -l' alias ll='ls -l --color=tty' alias r='fc -s' alias temp='cat /proc/acpi/thermal_zone/THM/temperature'
Create new alias named "memu" (see: awk example)
alias memu="awk -f /home/eberg/scripts/memu.awk"
Remove alias for "temp"
unalias temp
apropos
search manual pages names and descriptions
Show matching commands for stat in section 1 of the manual
apropos -s 1 stat acpi (1) - Shows battery status information kpsestat (1) - compute octal mode from mode of existing file lpq (1) - show printer queue status lpstat (1) - print cups status information mailstat (1) - shows mail-arrival statistics skill (1) - send a signal or report process status snice (1) - send a signal or report process status stat (1) - display file or file system status xtrapstats (1x) - XTrap sample clients
at
queue jobs for later execution
Schedule a task to run at 11:05 a.m.
at 11:05am
Schedule a task to run 24 hours from now
at tomorrow
Teatime? schedule a task to run at 4:00 p.m.
at teatime
Schedule a task to run five minutes from now
at now + 5 minutes
Print command for scheduled job 22 in queue
at -c 22
atq
show jobs in queue
List jobs in the at queue for current user (tmtowtdi: at -l)
atq 22 2006-02-15 11:05 a eberg 24 2006-02-15 16:00 a eberg 25 2006-02-15 09:13 a eberg 23 2006-02-16 09:08 a eberg
atrm
remove jobs from queue
Remove job ID from atq (tmtowtdi: at -r ID)
atrm ID
awk
pattern scanning and processing language
Print the login name and user's full name from /etc/passwd, separate output with a comma
awk -F: '{print $1 "," $5}' /etc/passwd | sort
ber,Brian Redman
bub,Bubbette McLeod
eb,Erik Berg
jmiz,John Mizel
sklarm,Mike Sklar
An awk for loop
awk 'BEGIN { for (i=1; i<=5; i++) print i }'
1
2
3
4
5
An awk while loop
awk 'BEGIN { i=1; while (i<=5) { print i; i++; } }'
1
2
3
4
5
Print amount of non-swapped physical memory (RSS) in use by current user
ps ux | awk '{ total += $6 } END { print "Mem usage: " total }'
Mem usage: 336128
More complex example of the above. Print physical memory usage of all users on system sorted by memory used. Save the following to a file named memu.awk
BEGIN {
ps = "ps -eo user,rss | sed 1d"
while ((ps | getline) > 0) {
memtotal[$1] += $2
}
close(ps)
for (name in memtotal)
printf("%-8s %10d\n", name, memtotal[name]) | "sort -k2 -rn"
}
Execute the script directly or save it to an alias
awk -f memu.awk eb 223420 root 81272 apache 45912 mysql 18492 ntp 4368 nscd 2556 xfs 1956 dbus 960 rpc 540
This example looks for 27/Apr in the web server log file. Then, it counts, sorts, and prints the IP address based on the number of times it showed up in the log
awk '/27\/Apr/ { num[$1]++ } \
END { for (ip in num) printf("%-15s %7d\n", ip, num[ip]) }' access_log|sort -k2 -n
66.x.65.19 10
192.x.112.194 11
24.x.217.45 11
66.x.103.72 14
70.x.17.225 15
206.x.249.251 16
64.x.85.75 17
Awk can be used to execute other commands with its system function. This is a crude and quick way to block the IP of a remote system launching PHP XML-RPC, drupal, mambo attacks
tail --follow=name /var/log/httpd/access_log | awk '/mambo|xmlrpc.php|drupal/ \
{ system("iptables -A INPUT -p tcp --dport 80 --source " $1 " -j DROP") }'
Sort disk usage output in human readable format. Change command to du -sb * to see actual file sizes, not the amount of disk being used. For greater precision, adjust the printf command. Save the following to a file named du.awk
#!/usr/bin/awk -f
BEGIN {
FS="\t" # separate fields by tabstops--don't put tabs in your filenames, haxor
du = "du -sB 1 * | sort -n"
while ((du | getline) > 0) {
if ($1 < 1024)
printf("%dB\t%s\n", $1, $2)
if (1024^1 <= $1 && $1 < 1024^2)
printf("%.0fK\t%s\n", $1/1024^1, $2)
if (1024^2 <= $1 && $1 < 1024^3)
printf("%.1fM\t%s\n", $1/1024^2, $2)
if (1024^3 <= $1)
printf("%.2fG\t%s\n", $1/1024^3, $2)
}
}
Execute the script directly. Note by including the shebang (#!/usr/bin/awk -f), it is not necessary to preclude awk -f on the command line
/home/eberg/scripts/du.awk 4K Makefile 28K CVS 28K robots 44K html 48K css 48K javascript 48K xsl 56K favicon 100K tools 1.5M notes
basename
strips directory paths from filenames
Remove leading directory and path information from NAME
basename /usr/bin/less less
tmtowtdi: instead of forking basename use a bash feature instead. ${VAR##*/} will remove everything up to and including the last slash "/" from VAR. (see also: dirname)
filename=/usr/share/man/man8/ping.8.gz
echo ${filename##*/}
ping.8.gz
When both a directory prefix and a suffix need to be stripped, basename can help. This removes the leading directory and path information as well as the .png suffix
basename /home/eb/erikberg.com/notes/i/w3m_url.png .png w3m_url
bc
an arbitrary precision calculator language
Start interactive bc session with a scale of 20
bc -l
Print 232 power
echo 2^32 | bc 4294967296
Print number of inches in a meter
echo 100/2.54 | bc -l 39.37007874015748031496
Convert 75 degrees Fahrenheit to Celsius (see: functions)
echo '(75-32)*(5/9)' | bc -l 23.88888888888888888865
bzip2
file compressor
Compress FILE
bzip2 FILE
Uncompress FILE.bz2
bunzip2 FILE.bz2
Uncompress bzipped tar archive FILE.tar.bz2
tar zjvf FILE.tar.bz2
Create bzipped tar archive FILE.tar.bz2 of the directory DIR
tar cjvf FILE.tar.bz2 DIR
cal
displays a calendar
Print previous, current, and next months
cal -3
January 2006 February 2006 March 2006
Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa
1 2 3 4 5 6 7 1 2 3 4 1 2 3 4
8 9 10 11 12 13 14 5 6 7 8 9 10 11 5 6 7 8 9 10 11
15 16 17 18 19 20 21 12 13 14 15 16 17 18 12 13 14 15 16 17 18
22 23 24 25 26 27 28 19 20 21 22 23 24 25 19 20 21 22 23 24 25
29 30 31 26 27 28 26 27 28 29 30 31
Display current month with Monday as the first day of the week
cal -m
February 2006
Mo Tu We Th Fr Sa Su
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28
cat
concatenate files and print on the standard output
Concatenate FILE1 and FILE2 into FILE3
cat FILE1 FILE2 > FILE3
Append FILE2 to the end of FILE1
cat FILE2 >> FILE1
Print FILE showing tab stops, ends of lines, and non-printing characters
cat -A FILE
Number each line in FILE (see also: nl)
cat -n FILE
The hacker's way to program "Hello, world"
cat <<eof
Hello, world
eof Hello, world
chkconfig
updates and queries runlevel information for system services
Print list of services from /etc/rc[0-6].d and their startup configurations
chkconfig --list
Show the startup configuration for the sendmail service
chkconfig --list sendmail sendmail 0:off 1:off 2:off 3:on 4:off 5:off 6:off
Enable SERVICE to start when system enters runlevels three and five
chkconfig --level 35 SERVICE on
chroot
change root directory
Switch the root directory to /mnt
chroot /mnt
comm
compare two sorted files line by line
Compare two sorted files. Given:
FILE1 FILE2 ----- ----- a d b e c f x x y y z z
Print lines that appear either in FILE1 or FILE2, but not both
comm -3 FILE1 FILE2
a
b
c
d
e
f
Print lines unique to FILE1 in first column, common to both FILES in second column
comm -2 FILE1 FILE2
a
b
c
x
y
z
Print lines unique to FILE2 in first column, common to both FILES in second column
comm -1 FILE1 FILE2
d
e
f
x
y
z
Print lines unique to FILE1 in first column, lines unique to FILE2 in second column, and lines common to both FILES in third column
comm FILE1 FILE2
a
b
c
d
e
f
x
y
z
convert
convert between image formats and much more
Copy and convert FILE.jpg to FILE.png
convert FILE.jpg FILE.png
cpio
copy files to and from archives
Copy all files in current directory and subdirectories to NEW_DIRECTORY
find . -depth -print0 | cpio -0pvd NEW_DIRECTORY
crontab
maintain and install crontab files
The original crontab author played a joke on every QWERTY keyboard user by making the options to modify a crontab file ( -e) and delete a crontab file ( -r) susceptible to disastrous typing mistakes. Because the chance to delete a crontab file accidentally instead of editing it is a simple mistype, I recommend always editing a local file and then using the crontab command to install it
crontab -l > crontab.0429
After making changes to the local file, install it
crontab crontab.0429
csplit
split a file based on a pattern
Create three files named xx00, xx01, and xx02 by splitting FILE on blank lines. Given FILE contains:
this will go to xx00 this will go to xx00 this will go to xx00 this will go to xx01 this will go to xx01 this will go to xx02 this will go to xx02 this will go to xx02 this will go to xx02
csplit FILE /^$/ {*}
63
43
85
cut
remove sections from each line of files
On line delimited by commas, print the 2nd and 5th fields
echo "1,2,3,4,5" | cut -d, -f2,5 2,5
Print the login name and user's full name from /etc/passwd, separate output with a tab
cut -d: -f1,5 --output-delimiter=" " /etc/passwd eberg Erik Berg
When dealing with a fixed width file with varying field lengths, cut works well on byte ranges. The following will print bytes 1-3 (the "RK" column) and bytes 23 to the end of the line (the "Pts" column). Given FILE contains:
RK Name Pts 1 Duke 1617 2 Michigan State 1558 3 Kansas State 1422 4 Ohio State 1379 5 Pittsburgh 1325 6 Villanova 1197 7 Kansas 1078 8 North Carolina 1021 9 Florida 989 10 Syracuse 967
cut -b1-3,23- FILE RK Pts 1 1617 2 1558 3 1422 4 1379 5 1325 6 1197 7 1078 8 1021 9 989 10 967
cvs
Concurrent Versions System
Show differences between working files and files in CVS repository
cvs diff -u
Show differences between revision 1.2 and 1.1 in FILE
cvs diff -u -r1.2 -r1.1 FILE
Print status information about files in working directory and CVS repository
cvs status
date
display or set the system date and time
Format date string in YYYYMMDD format to MM/DD/YY format
date -d 20070727 +"%m/%d/%y" 07/27/07
Same, but without padding
date -d 20070727 +"%-m/%-d/%y" 7/27/07
Print date three months from now
date -d '3 months' +"%b %-d, %Y" Oct 27, 2007
Print date three months ago
date -d '3 months ago' +"%b %-d, %Y" Apr 27, 2007
Print number of seconds since January 1, 1970 (epoch)
date +"%s" 1185525771
Display seconds since the epoch in a more human friendly format
date -d 'Jan 1 1970 1185525771 seconds' +"%A %B %-d, %Y" Friday July 27, 2007
dd
convert and copy a file
Create one megabyte file /tmp/foobar
dd if=/dev/zero of=/tmp/foobar bs=1024k cnt=1 1+0 records in 1+0 records out
df
report filesystem disk space usage
Print amount of disk space used and available on all filesystems
df -h Filesystem Size Used Avail Use% Mounted on /dev/hda3 9.7G 6.2G 3.1G 67% / /dev/hda1 99M 15M 80M 16% /boot none 501M 0 501M 0% /dev/shm
Print number of inodes available, used, and percentage used
df -i Filesystem Inodes IUsed IFree IUse% Mounted on /dev/hda3 1281696 296485 985211 24% / /dev/hda1 26104 43 26061 1% /boot none 128172 1 128171 1% /dev/shm
diff
find differences between two files
Show differences between files foo and foo.orig in format suitable for patch command
diff -u foo.ORIG foo
Compare files in two directories
diff DIR1 DIR2
dircolors
color setup for ls and other GNU commands
Print all color codes and default color settings for ls
dircolors -p
dirname
strips non-directory suffix from filenames
Remove filename from NAME
dirname /usr/bin/less /usr/bin
tmtowtdi: the same behavior can be duplicated by using a bash feature. ${VAR%/*} will start from the end of VAR and remove backwards up to and including the first slash "/" matched. (see also: basename)
filename=/usr/share/man/man8/ping.8.gz
echo ${filename%/*}
/usr/share/man/man8
dos2unix
convert DOS/MAC text files to UNIX
Convert FILE with carriage returns and newlines (\r\n) to newlines only (see also: unix2dos)
dos2unix FILE
du
estimate file space usage
Print amount of disk space used by files in the current directory and subdirectories
du -sh . 1.3M .
Print amount of disk space used by files in the current directory only--don't include subdirectories
du -sSh . 248K .
Print disk usage summary in kilobytes of all files and subdirectories in current directory, sorted by size. See awk example above for output in human readable format
du -sk * | sort -n 4 Makefile 28 CVS 28 robots 44 html 48 css 48 javascript 48 xsl 56 favicon 100 tools 1588 notes
dumpe2fs
Print ext2/ext3 filesystem information
Display detailed superblock information for device /dev/hda2. Useful, among other things, to show the block size of a filesystem
dumpe2fs -h /dev/hda2 dumpe2fs 1.32 (09-Nov-2002) Filesystem volume name: /d2 Last mounted on: <not available> Filesystem UUID: c1a10944-ab5e-40c9-9c3c-d658f0331dab Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal filetype needs_recovery sparse_super large_file Default mount options: (none) Filesystem state: clean Errors behavior: Continue Filesystem OS type: Linux Inode count: 13533184 Block count: 27059484 Reserved block count: 1352974 Free blocks: 4749268 Free inodes: 13256343 First block: 0 Block size: 4096 Fragment size: 4096 Blocks per group: 32768 Fragments per group: 32768 Inodes per group: 16384 Inode blocks per group: 512 Filesystem created: Wed Mar 24 10:51:56 2004 Last mount time: Fri Feb 17 12:52:17 2006 Last write time: Fri Feb 17 12:52:17 2006 Mount count: 17 Maximum mount count: -1 Last checked: Tue May 3 03:41:05 2005 Check interval: 0 (<none>) Reserved blocks uid: 0 (user root) Reserved blocks gid: 0 (group root) First inode: 11 Inode size: 128 Journal UUID: <none> Journal inode: 8 Journal device: 0x0000 First orphan inode: 0
dumpkeys
show keyboard translation tables (must be used on console)
Show all compose key combinations. The letters can be typed by pressing compose key, then modifer, then second modifer. See also: /usr/share/X11/locale/en_US.UTF-8/Compose
dumpkeys --compose-only compose '`' 'A' to 'À' compose '`' 'a' to 'à' compose '\'' 'A' to 'Á' compose '\'' 'a' to 'á' compose '^' 'A' to 'Â' compose '^' 'a' to 'â' compose '~' 'A' to 'Ã' compose '~' 'a' to 'ã' ...
echo
display a line of text
Display all commands in /usr/sbin and /usr/bin
echo /usr/sbin/* /usr/bin/*
Beep
echo -e '\a'
Do not print trailing newline character
echo -n No newline here
env
run a program in a modified environment
Print the current shell environment variables
env
Run COMMAND with the LANG environment variable value set to C
env LANG=C COMMAND
expr
evaluate arguments as an expression
Add 22 + 29
expr 22 + 29
Return length of string (tmtowtdi: wc -c)
expr length sweaterdresses 14
Return first 7 characters of string, first character begins at 1
expr substr sweaterdresses 1 7 sweater
fc
fix command
Show last 10 commands
fc -l -10
Create alias "r" that repeats last command in history that starts with STRING (tmtowtdi: !STRING)
alias r='fc -s'
r STRING
file
determine file type
Print type (binary, image, script, etc.) of file for FILE
file FILE
find
search for files in a directory hierarchy
Print filename and size of files ending in .png that are more than 100k and less than 200k
find . -name "*.png" -size +100k -size -200k -printf "%-60p %6s\n" ./software/qlcrash/logo2.png 166613 ./f1/montreal/raceday.png 118729 ./stats.png 104205 ./new.png 150399
Change files NOT owned by daemon to daemon
find . ! -user daemon -exec chown daemon {} \;
Change files that have permissions 777 (-rwxrwxrwx) to 644 (-rw-r--r--)
find . -perm 777 -exec chmod 644 {} \;
Print files in /var/log that were modified within the last 60 minutes
find /var/log -type f -mmin -60 /var/log/wtmp /var/log/messages /var/log/cron /var/log/sa/sa15
Search for files by their inode number
find . -inum 1550908 -ls 1550908 112 -rw-r--r-- 1 eberg users 104205 Feb 18 2005 ./stats.png
Find regular files that begin with a "." followed by an alphanumeric character in current directory only--don't descend into subdirectories
find . -maxdepth 1 -name ".[[:alnum:]]*" -type f
fuser
identify processes using files or sockets
Print the PID of the program using TCP port 22
fuser 22/tcp 22/tcp: 13272
Print the PID of the program using UDP port 123
fuser 123/udp 123/udp: 4222
Print the PIDs of the programs accessing /bin/bash in ps style
fuser /bin/bash -v
USER PID ACCESS COMMAND
/bin/bash eberg 26579 ...e. bash
eberg 26635 ...e. bash
root 26804 ...e. bash
Send SIGKILL signal to all processes that have /usr/share/YaST2 open
fuser -k /usr/share/YaST2
Send the preferred kill signal, SIGTERM, which gives processes a chance to cleanup properly
fuser -TERM -k /usr/bin/pine /usr/bin/pine: 30127e
gdb
the GNU Debugger
Start an interactive debugger session with PROGRAM
gdb PROGRAM
Start an interactive debugger session with PROGRAM and a CORE file
gdb PROGRAM CORE
getconf
Query system configuration variables
Print the maximum number of characters a command line can contain
getconf ARG_MAX 131072
For more operating system limits see /usr/include/linux/limits.h
grep
print lines matching a pattern
Count number of lines matching PATTERN in FILE
grep -c PATTERN FILE
Count number of lines NOT matching PATTERN in FILE
grep -cv PATTERN FILE
Count total number of instances PATTERN occurs in FILE, useful when PATTERN is repeated multiple times on a single line
grep -o PATTERN FILE | wc -l
Print lines in FILE that don't contain any digits
grep -v [[:digit:]] FILE
Perform a case insensitive search for PATTERN in FILE
grep -i PATTERN FILE
Sometimes it's useful to see the previous and following
lines after a match. This prints the two lines previous and the
two lines following a match of the string OpenLDAP in file
README
grep -C 2 OpenLDAP README If you are attempting to compile in the LDAP functionality in pine, you should get the OpenLDAP source, set up the libldap and liblber libraries, and the include files. A usually easy way to do that is -- using ldap-3.3. Alternatively, OpenLDAP may already be included in your system libraries. Solaris 8 is apparently set up this way. The script contrib/ldap-setup, which is called by the build script, tries to detect this automatically.
Print line number and lines matching string sm_strlcpy in file dkim-filter.c
grep -n sm_strlcpy dkim-filter.c 1348: sm_strlcpy(cc->cctx_host, host, sizeof cc->cctx_host); 1637: sm_strlcpy(addr, from->hdr_val, sizeof addr); 2288: sm_strlcpy(hdr, "unknown", sizeof hdr); 2289: sm_strlcpy(val, "unknown", sizeof val);
Set two environment variables to add a little color to grep
matches. GREP_COLOR will highlight matches in the specified
color. Settings specified in GREP_OPTIONS will be used with
each grep invocation. (see:
dircolors for color codes)
export GREP_COLOR=01\;34 export GREP_OPTIONS=--color=auto grep color tips.css color: #000000; a:visited { color: #80080; } background-color:green; color:#ffffff; background-color: #080; color:#080; color:#080; background-color:white; grep -C 1 OpenLDAP README If you are attempting to compile in the LDAP functionality in pine, you should get the OpenLDAP source, set up the libldap and liblber libraries, and the include files. A usually easy way to do that is -- Alternatively, OpenLDAP may already be included in your system libraries. Solaris 8 is apparently set up this way. The script contrib/ldap-setup,
The -o option will print only the matched
PATTERN on a line. Useful when matching on very long lines
grep -o PATTERN FILE
gzip
compress or expand files
compress FILE
gzip FILE
uncompress FILE_GZ
gzip -d FILE_GZ
Uncompress gzipped tar archive TAR_GZ
tar zxvf TAR_GZ
Create gzipped tar archive FILE_TAR_GZ of the directory DIR
tar czvf FILE_TAR_GZ DIR
hdparm
get/set hard disk parameters
Show hard drive settings for /dev/hda
hdparm /dev/hda /dev/hda: multcount = 16 (on) IO_support = 0 (default 16-bit) unmaskirq = 0 (off) using_dma = 1 (on) keepsettings = 0 (off) readonly = 0 (off) readahead = 256 (on) geometry = 58140/16/63, sectors = 30005821440, start = 0
Print performance statistics about /dev/hda hard drive
hdparm -tT /dev/hda /dev/hda: Timing cached reads: 1232 MB in 2.00 seconds = 615.96 MB/sec Timing buffered disk reads: 74 MB in 3.04 seconds = 24.34 MB/sec
head
output the first part of files
Print the first 20 lines in FILE
head -20 FILE
Print lines 15-20 in FILE (tmtowtdi: sed -n 15,20p FILE)
head -20 FILE | tail -5
iconv
convert character encoding in file to another
Convert FILE from iso-8859-1 encoding to utf-8 encoding
iconv -f ISO-8859-1 -t UTF-8 FILE
Print list of coded character set names that can be used with -f and -t options
iconv -l
ident
identify RCS keyword strings in files
Show RCS keywords in file linuxtips.html
ident linuxtips.html
linuxtips.html:
$Id: linuxtips.html,v 1.118 2013/01/15 20:22:52 eb Exp $
ipcs
provide information on ipc facilities
Show shared memory, semaphore, and message queue information
ipcs ------ Shared Memory Segments -------- key shmid owner perms bytes nattch status 0x00000000 1409024 root 600 33554432 9 dest 0x00000000 1245185 root 600 262144 1 dest ------ Semaphore Arrays -------- key semid owner perms nsems 0x00000000 458752 httpd 600 1 0x00000000 491521 httpd 600 1 0x00000000 524290 httpd 600 1 ------ Message Queues -------- key msqid owner perms used-bytes messages 0x00001f58 0 root 600 0 0
ipcrm
remove a message queue, semaphore set or shared memory id
Remove the shared memory segment SHMID from the system
ipcrm -m SHMID
join
join lines of two files on a common field
Given:
FILE1 FILE2 ----- ----- 1 abc 1 def 2 ghi 2 jkl 3 mno 3 pqr 4 stu 4 vwx 5 yz
Join FILE1 and FILE2 on their common fields (i.e., 1-4)
join FILE1 FILE2 1 abc def 2 ghi jkl 3 mno pqr 4 stu vwx
Same, but also print lines from FILE1 that have no match
join -a1 FILE1 FILE2 1 abc def 2 ghi jkl 3 mno pqr 4 stu vwx 5 yz
Print lines from FILE1 that have no common field match in FILE2
join -v1 FILE1 FILE2 5 yz
kbdrate
reset the keyboard repeat rate and delay time
Show the current keyboard delay and repeat settings (For X Windows see: xset)
kbdrate Typematic Rate set to 10.9 cps (delay = 250 ms)
Set the repeat rate for keyboard to 30.0 characters per second
kbdrate -r 30.0 Typematic Rate set to 30.0 cps (delay = 250 ms)
kill
send signal to a process
Suspend process PID
kill -STOP PID
Continue suspended process PID
kill -CONT PID
Print list of of valid signals
kill -l 1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL 5) SIGTRAP 6) SIGABRT 7) SIGBUS 8) SIGFPE 9) SIGKILL 10) SIGUSR1 11) SIGSEGV 12) SIGUSR2 ...
The null signal, often used in scripts. Tests for valid PID
kill -0 PID
kpartx
create device maps from partition tables
Add map for LV /dev/system/bob. After this command is run, /dev/mapper/system-bob1 can be mounted.
kpartx -v -a /dev/system/bob add map system-bob1 : 0 41929587 linear /dev/system/bob 63
Delete map for LV /dev/system/bob
kpartx -v -d /dev/system/bob del devmap : system-bob1
last
show listing of last logged in users
Show last five logins on system
last -5 eberg pts/5 :0.0 Sat Feb 11 14:56 still logged in eberg pts/4 :0.0 Sat Feb 11 14:48 still logged in eberg pts/3 :0.0 Sat Feb 11 14:32 still logged in eberg pts/3 :0.0 Sat Feb 11 14:27 - 14:27 (00:00) eberg pts/2 :0.0 Sat Feb 11 14:26 still logged in wtmp begins Wed Feb 2 11:32:46 2005
Show last four reboots on system with kernel information
last -4 reboot reboot system boot 2.6.5-7.201-defa Mon Sep 5 10:49 (172+21:09) reboot system boot 2.6.5-7.193-defa Tue Aug 9 16:27 (26+06:46) reboot system boot 2.6.5-7.155.29-d Wed Jul 20 17:51 (46+05:22) reboot system boot 2.6.5-7.151-defa Sat Mar 26 02:06 (162+20:07) wtmp begins Wed Feb 2 11:32:46 2005
ldconfig
configure dynamic linker run time bindings
After updating /etc/ld.so.conf this reads and updates /etc/ld.so.cache
ldconfig
Print list of libraries referenced in /etc/ld.so.cache
ldconfig -p 1062 libs found in cache `/etc/ld.so.cache' libz.so.1 (libc6) => /usr/lib/libz.so.1 libz.so (libc6) => /usr/lib/libz.so libx11globalcomm.so.1 (libc6) => /usr/lib/libx11globalcomm.so.1 libxslt.so.1 (libc6) => /usr/lib/libxslt.so.1 ...
less
file pager
Page through FILE
less FILE
locate
print location of files on system
Print STRING in locate database
locate strcpy /usr/lib/perl5/5.8.6/i386-linux-thread-multi/auto/POSIX/strcpy.al /usr/share/man/man3p/strcpy.3p.gz /usr/share/man/man3/strcpy.3.gz
logger
a shell command interface to syslog
Record MESSAGE to syslog
logger log some interesting info about a process or system status tail -1 /var/log/messages Mar 2 08:25:22 for eb: log some interesting info about a process or system status
look
display lines beginning with a given string
Show all words that match STRING at beginning of lines in /usr/share/dict/words
look usef useful usefullish usefully usefulness
ls
list directory contents
List files, sorted by size
ls -lS total 24 -rw-rw-r-- 1 eb eb 7584 Feb 11 02:10 trim.html drwxrwxr-x 2 eb eb 4096 Feb 14 18:21 CVS -rw-rw-r-- 1 eb eb 247 May 2 2005 Makefile -rw-rw-r-- 1 eb eb 0 Feb 13 19:40 index.html
List files, reverse sorted by file timestamp
ls -ltr total 24 -rw-rw-r-- 1 eb eb 247 May 2 2005 Makefile -rw-rw-r-- 1 eb eb 7584 Feb 11 02:10 trim.html -rw-rw-r-- 1 eb eb 0 Feb 13 19:40 index.html drwxrwxr-x 2 eb eb 4096 Feb 14 18:21 CVS
List inodes of files
ls -i 1569885 CVS 1570178 index.html 98129 Makefile 556185 trim.html
List file timestamps in very detailed ISO-8601 format
ls -l --time-style=full-iso total 24 drwxrwxr-x 2 eb eb 4096 2006-02-14 18:21:54.000000000 -0800 CVS -rw-rw-r-- 1 eb eb 0 2006-02-13 19:40:44.000000000 -0800 index.html -rw-rw-r-- 1 eb eb 247 2005-05-02 15:09:31.000000000 -0700 Makefile -rw-rw-r-- 1 eb eb 7584 2006-02-11 02:10:58.000000000 -0800 trim.html
File timestamps can be printed in almost any format using date formatting. This prints the timestamp in MM/DD/YY format
ls -l --time-style="+%m/%d/%y" total 24 drwxr-xr-x 2 eb eb 4096 02/14/06 CVS -rw-r--r-- 1 eb eb 0 02/13/06 index.html -rw-r--r-- 1 eb eb 247 05/02/05 Makefile -rw-r--r-- 1 eb eb 7584 02/11/06 trim.html
List all files that begin with 2007, but don't end with .jpg via extended shell globbing (i.e., shopt -s extglob)
ls 2007* 2007.txt 20070703.jpg 20070722.jpg 20070914.jpg 20071119.jpg 20070408.gif 20070703.png 20070722.png 20070914.png 20071119.png ls 2007!(*.jpg) -bash: !: event not found shopt -s extglob ls 2007!(*.jpg) 2007.txt 20070408.gif 20070703.png 20070722.png 20070914.png 20071119.png
lsmod
program to show the status of modules in the Linux Kernel
List currently loaded kernel modules (tmtowtdi: cat /proc/modules)
lsmod Module Size Used by i2c_dev 10049 0 i2c_core 21697 1 i2c_dev sunrpc 146045 1 pcmcia 38781 2 ...
lsof
list open files
List all open files on system
lsof
List all IPv4 network files in use (-i6 shows IPv6)
lsof -i 4 COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME portmap 1969 rpc 3u IPv4 5044 UDP *:sunrpc portmap 1969 rpc 4u IPv4 5048 TCP *:sunrpc (LISTEN) nscd 2039 nscd 3u IPv4 5409 TCP for.ebloft.sea:60484->fore.ebloft.sea:ldap (ESTABLISHED) ntpd 2074 ntp 4u IPv4 5350 UDP *:ntp ntpd 2074 ntp 7u IPv4 5378 UDP for.ebloft.sea:ntp mysqld 2165 mysql 3u IPv4 5399 TCP *:mysql (LISTEN) bash 2837 eb 4u IPv4 15702 TCP for.ebloft.sea:53903->fore.ebloft.sea:ldap (ESTABLISHED) ssh 3368 eb 3u IPv4 10624 TCP for.ebloft.sea:46982->fore.ebloft.sea:ssh (ESTABLISHED)
List all open files using port 22 (SSH)
lsof -i :22
Same as above, but using the service name instead of the port number
lsof -i :ssh
List all files in use for process that begins with STRING
lsof -c STRING
List all processes and files accessing directory /tmp
lsof +d /tmp COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME gnome-key 3592 eb 3u unix 0xd8755200 9806 /tmp/keyring-pAmjqz/socket firefox-b 19833 eb 169u unix 0xca103e00 115000 /tmp/jpsock.150_06.19833 firefox-b 19833 eb 173u unix 0xd1e60b00 115021 /tmp/jpsock.150_06.19833 mapping-d 22849 eb 3u unix 0xce458800 56398 /tmp/mapping-eb mapping-d 22849 eb 4u unix 0xce458980 56402 /tmp/mapping-eb
List all processes and files accessing directory and subdirectories of /tmp
lsof +D /tmp COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME java_vm 25068 eb mem REG 3,3 32768 261148 /tmp/hsperfdata_eb/25068 gconfd-2 26703 eb 10u unix 0xcf358c80 76405 /tmp/orbit-eb/linc-684f-0-23d1a1aec6f86 gconfd-2 26703 eb 12u unix 0xd3873380 76092 /tmp/orbit-eb/linc-684f-0-23d1a1aec6f86 gconfd-2 26703 eb 13wW REG 3,3 602 182541 /tmp/gconfd-eb/lock/ior gconfd-2 26703 eb 15u unix 0xcf25ec80 83237 /tmp/orbit-eb/linc-684f-0-23d1a1aec6f86 gconfd-2 26703 eb 17u unix 0xd3873680 85278 /tmp/orbit-eb/linc-684f-0-23d1a1aec6f86 gconfd-2 26703 eb 31u unix 0xcb2afb00 91912 /tmp/orbit-eb/linc-684f-0-23d1a1aec6f86 gconfd-2 26703 eb 33u unix 0xcb2af680 109082 /tmp/orbit-eb/linc-684f-0-23d1a1aec6f86 notificat 29242 eb 15u unix 0xc4733c80 34965 /tmp/orbit-eb/linc-723a-0-2b8ed990d27da notificat 29242 eb 16u unix 0xc4733b00 34968 /tmp/orbit-eb/linc-723a-0-2b8ed990d27da notificat 29242 eb 19u unix 0xc291f500 76121 /tmp/orbit-eb/linc-723a-0-2b8ed990d27da ...
List all files in use by process PID
lsof -p PID
List all files in use by USER
lsof -u USER
Send kill signal to all (mail) processes on port 25
kill -HUP $(lsof -t -i :25)
lspci
list all PCI devices
List PCI devices on system
lspci 00:00.0 Host bridge: Intel Corporation 82845 845 (Brookdale) Chipset Host Bridge (rev 04) 00:01.0 PCI bridge: Intel Corporation 82845 845 (Brookdale) Chipset AGP Bridge (rev 04) ...
Show information about device using address 00:01 in extra verbose (-vv) format
lspci -vv -s 00:01
00:01.0 PCI bridge: Intel Corporation 82845 845 (Brookdale) Chipset AGP Bridge (rev 04)
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+
Status: Cap- 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort-
Latency: 32
Bus: primary=00, secondary=01, subordinate=01, sec-latency=32
I/O behind bridge: 0000c000-0000cfff
Memory behind bridge: fc000000-fdffffff
Prefetchable memory behind bridge: f0000000-f3ffffff
Secondary status: 66MHz+ FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort-
BridgeCtl: Parity- SERR- NoISA+ VGA+ MAbort- >Reset- FastB2B-
lsusb
list USB devices
List USB devices on system (tmtowtdi: cat /proc/bus/usb/devices)
lsusb Bus 004 Device 001: ID 0000:0000 Bus 003 Device 001: ID 0000:0000 Bus 002 Device 001: ID 0000:0000 Bus 001 Device 001: ID 0000:0000
ltrace
library call tracer
Trace all library calls made by COMMAND
ltrace echo "Hello, world"
__libc_start_main(0x8048ea5, 2, 0xbffd9df4, 0x804a67c, 0x804a6cc <unfinished ...>
setlocale(6, "") = "en_US.UTF-8"
bindtextdomain("coreutils", "/usr/share/locale") = "/usr/share/locale"
textdomain("coreutils") = "coreutils"
__cxa_atexit(0x8049309, 0, 0, 0x804c85c, 0xbffd9d68) = 0
getenv("POSIXLY_CORRECT") = NULL
getopt_long(2, 0xbffd9df4, "+", 0x804c700, NULL) = -1
fputs_unlocked(0xbffdb9f5, 0x2365e0, 0x804aad1, 0x804aac3, 0x804aabd) = 1
__overflow(0x2365e0, 10, 0x804aad1, 0x804aac3, 0x804aabdHello, world
) = 10
exit(0 <unfinished ...>
__fpending(0x2365e0, 0x72b878, 0xb7fdc6a0, 1, 1) = 0
+++ exited (status 0) +++
Print nice summary table of all library calls made by COMMAND
ltrace -c echo "Hello, world" Hello, world % time seconds usecs/call calls function ------ ----------- ----------- --------- -------------------- 47.55 0.000806 806 1 setlocale 17.94 0.000304 304 1 __overflow 11.03 0.000187 187 1 fputs_unlocked 4.72 0.000080 80 1 getopt_long 3.89 0.000066 66 1 __fpending 3.83 0.000065 65 1 bindtextdomain 3.72 0.000063 63 1 textdomain 3.72 0.000063 63 1 __cxa_atexit 3.60 0.000061 61 1 getenv ------ ----------- ----------- --------- -------------------- 100.00 0.001695 9 total
man
format and display the on-line manual pages
Display manual page for COMMAND
man COMMAND
Display man page for waitpid in section 3p
man 3p waitpid
Return list of man pages that contain STRING (tmtowtdi: apropos STRING)
man -k STRING
md5sum
compute and check MD5 message digest
Print MD5 checksum for FILE
md5sum FILE
Save output from md5sum to FILE. Use the --check option in conjunction with FILE to determine whether the MD5 checksums have changed.
md5sum linuxtips.html Makefile milters.html > FILE md5sum --check FILE linuxtips.html: OK Makefile: OK milters.html: OK
metamail
Consults mailcap file to determine how to display non-text (e.g., MIME) encoded files
Decode MIME message contained in FILE
metamail FILE
modinfo
program to show information about a Linux Kernel module
Print information about kernel MODULE
modinfo MODULE
Print information about all currently active kernel modules on system
awk '{ print $1 }' /proc/modules | while read module; do
modinfo $module
echo -e '\n======================\n'
done
mount
mount and unmount a filesystem
Mount /dev/dvd to /mnt
mount /dev/dvd /mnt
Make /dev available to /mnt/dev. Sometimes useful when working in chroot environments when access to files like /dev/urandom is needed
mount --bind /dev /mnt/dev
namei
follow a pathname until a terminal point is found
Follow symbolic link until an end point is found
namei /bin/sh f: /bin/sh d / d bin l sh -> bash - bash
nice
run a program with modified scheduling priority
Run COMMAND at priority 19 (the lowest)
nice -n 19 COMMAND
nl
number lines of files
Number each non-empty line in FILE (tmtowtdi: cat -b)
nl FILE
Number each line in FILE (tmtowtdi: cat -n)
nl -ba FILE
nroff
shell script frontend to groff
print and format manual page for nice
zcat nice.1.gz | nroff -man | less
ntpq
standard NTP query program
Print NTP peer status
ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
*fore.ebloft.sea xx.71.9.63 4 u 68 256 377 0.827 -12.692 7.887
ntpstat
show network time synchronization status
Display NTP synchronization status
ntpstat synchronised to NTP server (192.168.1.151) at stratum 5 time correct to within 114 ms polling server every 256 s
od
dump files in octal and other formats
Print FILE in octal
od FILE
paste
merge lines of files
Merge lines of FILE1 FILE2
paste FILE1 FILE2
Merge lines in FILE separated by tabs. Given FILE contains:
Long Beach Huntington Beach Newport Beach Laguna Beach
paste - - - < FILE Long Beach Huntington Beach Newport Beach Laguna Beach
patch
apply a diff file to an original file
Create a diff file between ORIGINAL and NEWFILE, then apply the changes in NEWFILE to ORIGINAL
diff -u ORIGINAL NEWFILE > CHANGES.patch patch -p0 < CHANGES.patch
perldoc
Look up Perl documentation in Pod format
Display documentation for module IO::File
perldoc IO::File
pgrep
look up or signal processes based on name and other attributes
Print Process IDs matching PATTERN
pgrep PATTERN
Pass output from pgrep to ps for a full listing (see: functions to make this easily accessible)
ps uwp $(pgrep httpd) USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 2028 0.0 1.9 21896 9872 ? Ss 06:45 0:00 /usr/sbin/httpd apache 2032 0.0 0.5 18244 2728 ? S 06:45 0:00 /usr/sbin/fcgi- apache 2055 0.0 1.0 21896 5380 ? S 06:45 0:00 /usr/sbin/httpd apache 2056 0.0 1.0 21896 5380 ? S 06:45 0:00 /usr/sbin/httpd
pinfo
curses based lynx-style info browser
Display Info document for COMMAND, most GNU commands are distributed with Info pages (see: info). Screenshot
pinfo COMMAND
printf
format and print data
Print thousands' grouping character (dependent on locale)
printf "%'d\n" $(echo 2^32 | bc) 4,294,967,296
Left pad number with zeros (tmtowtdi: seq -f "%05g" 1 5)
for ((i=1;i<=5;i++)) do printf "%05d\n" $i done 00001 00002 00003 00004 00005
Print 1048576 in hexadecimal
printf "%x\n" 1048576 100000
Same, but precede output with '0x'
printf "%#x\n" 1048576 0x100000
Print 1048576 in octal
printf "%o\n" 1048576 4000000
Same, but precede output with '0'
printf "%#o\n" 1048576 04000000
Print hex value 0xff in decimal
printf "%d\n" 0xff 255
Print octal value 0377 in decimal
printf "%d\n" 0377 255
Print ascii characters for hex values 0x68, 0x74, 0x74, 0x70
printf "\x68\x74\x74\x70" http
Print ascii character for decimal value 84
printf $(printf "\%o" 84) T
ps
report a snapshot of the current processes
Report all running processes on the system UNIX System V style in long format
ps -efl F S UID PID PPID C PRI NI ADDR SZ WCHAN STIME TTY TIME CMD 4 S root 1 0 0 75 0 - 377 - Feb09 ? 00:00:36 init 5 S root 2 0 0 -40 0 - 0 - Feb09 ? 00:00:00 [migration/0]
Report all running processes on the system BSD-style in "unlimited width" output
ps auxww USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.0 0.0 1508 512 ? S Feb09 0:36 init root 2 0.0 0.0 0 0 ? SW Feb09 0:00 [migration/0]
Show all processes owned by USER
ps -fu ldap UID PID PPID C STIME TTY TIME CMD ldap 4506 1 0 Feb17 ? 00:02:04 /usr/sbin/slapd -u ldap -h ldap:/// ldaps:///
pstree
pwd
print working directory
An often overlooked option for the bash pwd builtin is -P which prints the absolute working directory. Compare:
pwd /usr/src/linux pwd -P /usr/src/linux-2.4.21-20.EL
renice
alter priority of running processes
Lower scheduling priority of all processes owned by USER
renice 10 -u USER
As root, increase scheduling priority of running process PID
renice -10 -p PID
rev
reverse lines of a file
Reverse the characters on each line in FILE
rev FILE
rpm
Red Hat Package Manager
Print what RPM package contains FILE
rpm -qf FILE
It is often useful to use the -qf options with which when trying to determine the package owner for a command
rpm -qf $(which df) coreutils-5.2.1-48.1
Print information about RPM_PACKAGE
rpm -qi RPM_PACKAGE
List files in RPM_PACKAGE
rpm -ql RPM_PACKAGE
Install or Upgrade RPM_PACKAGE, ignore any dependencies
rpm -Uvh --nodeps RPM_PACKAGE
rsync
faster, flexible replacement for rcp
Synchronize files in LOCALDIR to HOST in REMOTEDIR
rsync -e ssh --delete -avzP LOCALDIR HOST:REMOTEDIR
scl
manage software collections (RHEL)
List installed software collections
scl -l nodejs010 v8314
Configure nodejs010 environment to use in current bash shell
scl enable nodejs010 bash
script
make typescript of terminal session
Start a new shell where all input and output is saved to FILE
script FILE
scriptreplay
playback a typescript session at the same speed it was recorded
Save time information to TIMING and typescript to TYPESCRIPT.
script -t 2>TIMING TYPESCRIPT
After ending the typescript session, replay it using the following command.
scriptreplay TIMING TYPESCRIPT
sed
text editor
Edit FILE1, FILE2, FILE3 in place, replacing all occurrences of "iso-8859-1" with "UTF-8"
sed -i 's/iso-8859-1/UTF-8/g' FILE1 FILE2 FILE3
Print all lines that match PATTERN in FILE (tmtowtdi: grep)
sed -n '/PATTERN/p' FILE
Print all lines that don't match PATTERN in FILE (tmtowtdi: grep -v)
sed -n '/PATTERN/!p' FILE
Insert text "<!DOCTYPE html" at the first line in all files ending in .html
sed -i '1i <!DOCTYPE html' *.html
Append text "this is the last line" to the end of FILE
sed -i '$a this is the last line' FILE
Delete lines 1-5 from FILES
sed 1,5d FILES
Print all lines in syslog that were recorded from 10PM-2AM between February 15 and February 16
sed -n '/^Feb 15 22:/,/^Feb 16 02:/p' /var/log/messages | sed '$d'
Print lines line matching PATTERN and next five lines (tmtowtdi: grep -A 5 PATTERN FILE)
sed -n '/PATTERN/,+5p' FILE
Excellent resource for one-line sed scripts can be found at http:// pement.org/sed/ sed1line.txt
seq
print a sequence of numbers
Print numbers one through five
seq 1 5 1 2 3 4 5
tmtowtdi: use a bash feature for simple sequences, {x..y} where x and y are integers will expand to print each number between x and y (see also: looping)
for i in {1..5}
do
echo $i
done
1
2
3
4
5
Print numbers 25-50, iterate by 5, separate output with space
seq -s' ' 25 5 50 25 30 35 40 45 50
Print numbers 5 million to 10 million, increment by 1 million, using thousands grouping separator
seq -f "%'.f" 5000000 1000000 10000000 5,000,000 6,000,000 7,000,000 8,000,000 9,000,000 10,000,000
Print numbers from 0-255 in hexadecimal
printf "%x\n" $(seq 0 255) 0 1 ... fe ff
sfdisk
view (and set) partition information
List partitions on /dev/hda
sfdisk -l /dev/hda Disk /dev/hda: 58140 cylinders, 16 heads, 63 sectors/track Warning: The partition table looks like it was made for C/H/S=*/255/63 (instead of 58140/16/63). For this listing I'll assume that geometry. Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting from 0 Device Boot Start End #cyls #blocks Id System /dev/hda1 * 0+ 12 13- 104391 83 Linux /dev/hda2 13 3647 3635 29198137+ 8e Linux LVM /dev/hda3 0 - 0 0 0 Empty /dev/hda4 0 - 0 0 0 Empty
Print total size of /dev/hda in 1K blocks. tmtowtdi: cat /proc/ide/hda/capacity (512-byte blocks)
sfdisk -s /dev/hda 29302560
sha256sum
print and check SHA256 message digest
Print SHA256 checksum for FILE
sha256sum FILE b10bdb5dc695a9b182f7372a79e85c72a4455a538907bf59e5962bed6401cfa4 FILE
Verify that the checksums listed in file match what is on disk. Given a file named CHECKSUM contains:
55550e8b46b3a8080c4722ae87c5cafc60bb51778fe534760bee5775221393af config.json 4ce3a8c8c11cd39de9967e4e81b13a76797d230a3ed0b2e78288106db085ff81 package.json b3081f23981cb8eeed773303edb56e08009ceb5ab9029bd82736130bb0edaae4 xmlstats-proxy.js
sha256sum -c CHECKSUM config.json: OK package.json: OK xmlstats-proxy.js: OK
shuf
randomly sort input lines
Randomly sort lines in FILE
shuf FILE
Randomly sort lines in FILE, limit output to 10 lines
shuf -n 10 FILE
smartctl
print and set configuration for SMART disks
Print information about device
smartctl -i /dev/sda smartctl version 5.37 [i686-suse-linux-gnu] Copyright (C) 2002-6 Bruce Allen Home page is http://smartmontools.sourceforge.net/ === START OF INFORMATION SECTION === Model Family: Hitachi Travelstar 7K100 Device Model: HTS721010G9SA00 Serial Number: MPDZN7Y0J8R6SL Firmware Version: MCZIC15V User Capacity: 100,030,242,816 bytes Device is: In smartctl database [for details use: -P show] ATA Version is: 7 ATA Standard is: ATA/ATAPI-7 T13 1532D revision 1 Local Time is: Tue Oct 16 17:09:44 2007 PDT SMART support is: Available - device has SMART capability. SMART support is: Enabled
sort
sort lines of text files
Sort, merge, and remove duplicate entries from FILE1 and FILE2
sort -mu FILE1 FILE2
Sort on the first character in the fourth field using the underscore as the field separator
ls -1 *xml 20050425_ARI_at_LAD.xml 20050425_ATL_at_NYM.xml 20050425_BAL_at_BOS.xml 20050425_CHW_at_OAK.xml 20050425_CIN_at_CHC.xml 20050425_HOU_at_PIT.xml 20050425_MIN_at_DET.xml 20050425_PHI_at_WAS.xml 20050425_SD_at_SF.xml ls *xml | sort -t _ -k4.1 20050425_BAL_at_BOS.xml 20050425_CIN_at_CHC.xml 20050425_MIN_at_DET.xml 20050425_ARI_at_LAD.xml 20050425_ATL_at_NYM.xml 20050425_CHW_at_OAK.xml 20050425_HOU_at_PIT.xml 20050425_SD_at_SF.xml 20050425_PHI_at_WAS.xml
split
split a file into pieces
Break up LARGEFILE into 10MB files named xaa, xab, xac, ... (use cat to reconstruct LARGEFILE)
split --bytes=10m LARGEFILE
Split FILE into 100 line files named xaa, xab, xac, ...
split -l 100 FILE
stat
Report detailed file or filesystem information
Display access, size, inode, permission, etc. information for file linuxtips.html
stat linuxtips.html File: `linuxtips.html' Size: 73850 Blocks: 160 IO Block: 4096 regular file Device: fd00h/64768d Inode: 6870173 Links: 1 Access: (0664/-rw-rw-r--) Uid: ( 500/ eb) Gid: ( 100/ eb) Access: 2006-03-03 10:09:00.000000000 -0800 Modify: 2006-03-03 09:34:05.000000000 -0800 Change: 2006-03-03 09:34:05.000000000 -0800
Display information about FILESYSTEM
stat -f /
File: "/"
ID: 0 Namelen: 255 Type: ext2/ext3
Blocks: Total: 6808543 Free: 1013789 Available: 662353 Size: 4096
Inodes: Total: 7031360 Free: 6755474
strace
trace system calls and signals
Trace system calls for already running process PID
strace -f -s 1024 -p PID
Trace system calls for command ls, send strace output to /tmp/lsout
strace -f -s 1024 -o /tmp/lsout ls
strings
print the strings of printable characters in files
Extract printable characters from binary FILE
strings FILE
sysctl
get and set system parameters
Print all keys and values
sysctl -a
Print keys and values for file system parameters only
sysctl fs
Print value for SHMMAX (tmtowtdi: cat /proc/sys/kernel/shmmax)
sysctl kernel.shmmax kernel.shmmax = 4294967295
Disable IPv6 forwarding (tmtowtdi: echo 0 > /proc/sys/net/ipv6/conf/all/forwarding)
sysctl -w net.ipv6.conf.all.forwarding=0 net.ipv6.conf.all.forwarding = 0
tac
concatenate and print files in reverse
Print FILE in reverse
tac FILE
An early MSFT encryption algorithm? :-)
tac FILE | rev
tail
output the last part of files
Print the last 30 lines of /var/log/messages and all new lines as the file grows
tail -30f /var/log/messages
Print the first 20 of the last 50 lines in FILE
tail -50 FILE | head -20
Continue to print all new lines of access_log even when file is archived and recreated by another process. The default behavior of tail is to follow a file descriptor, not a filename
tail --follow=name /var/log/httpd/access_log
tar
create and extract archives
Create new archive named example.tar consisting of all files in DIRECTORY
tar cvf example.tar DIRECTORY
Create new gzip-compressed archive named example.tar.gz consisting of all files in DIRECTORY
tar czvf example.tar.gz DIRECTORY
List contents of example.tar archive
tar tvf example.tar
List contents of gzip-compressed example.tar.gz archive
tar tzvf example.tar.gz
Extract contents of example.tar archive
tar xvf example.tar
tee
read from standard input and write to standard output and files
Write standard output from COMMAND to standard out and FILE
COMMAND | tee FILE
time
time a simple command or give resource usage
Display system, user, and elapsed real time from executing COMMAND
time uptime 07:38:26 up 53 min, 3 users, load average: 0.18, 0.15, 0.15 real 0m0.008s user 0m0.000s sys 0m0.004s
tnef
decode MSFT Transport Neutral Encapsulation Format (TNEF)
Display attachment names contained in winmail.dat file
tnef -t winmail.dat
Extract attachments contained in winmail.dat file
tnef winmail.dat
touch
change file timestamps
Create empty NEW_FILE
touch NEW_FILE
Set existing FILE's access and modification times to now
touch FILE
Create or set existing FILE's access and modification times to May 1 2:20 p.m. and 15 seconds
touch -d 'May 1 14:20:15' FILE
tput
print/query terminal settings
Print number of columns for the current terminal
tput cols
man terminfo for list of tput capability names
tr
translate or delete characters
Delete all lowercase vowels from standard input
tr -d aeiou <<eof This command will remove all of the vowels from this sentence--just like people who send text messages! eof Ths cmmnd wll rmv ll f th vwls frm ths sntnc--jst lk ppl wh snd txt mssgs!
Convert all newlines to commas in FILE
tr '\n' ',' <FILE
ulimit
get and set user limits
Display all settings for current user
ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited file size (blocks, -f) unlimited pending signals (-i) 8186 max locked memory (kbytes, -l) 32 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 stack size (kbytes, -s) 10240 cpu time (seconds, -t) unlimited max user processes (-u) 8186 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited
uniq
repeat or omit duplicate lines
Check for duplicate lines from the tenth field onward in FILE. Fields are separated by a space
uniq -f 10 FILE
Count frequency of words in FILE. Note this uses a simple pattern match for finding individual words, it will produce incorrect results for words containing punctuation such as hyphens and apostrophes. Given FILE contains:
Around the world, around the world Around the world, around the world Around the world, around the world Around the world, around the world Around the world, around the world Around the world, around the world Around the world, around the world Around the world, around the world Around the world, around the world Around the world, around the world Around the world, around the world Around the world, around the world
tr -cs '[:alpha:]' '\n' < FILE | tr A-Z a-z | sort | uniq -c | sort -k2 -n 24 around 24 the 24 world
unix2dos
convert UNIX text files to DOS/MAC
Convert FILE with newlines only to DOS format with carriage returns and newlines (see also: dos2unix)
unix2dos FILE
update- alternatives
configure symbolic links for default commands
Display system settings for java
update-alternatives --display java java - status is auto. link currently points to /usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre/bin/java /usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre/bin/java - priority 9 Current `best' version is /usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre/bin/java.
Create or update link /usr/bin/java to point to a java binary installed under /opt/java/jsdk5.0/jdk/bin/java and a slave link for the manual page.
update-alternatives --install /usr/bin/java java /opt/java/jsdk5.0/jdk/bin/java 100 \ --slave /usr/share/man/man1/java.1 java.1 /opt/java/jsdk5.0/jdk/man/man1/java.1
Select which java version system link (/usr/bin/java) should use.
update-alternatives --config java
There are 2 programs which provide `java'.
Selection Command
-----------------------------------------------
1 /usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre/bin/java
*+ 2 /opt/java/jsdk5.0/jdk/bin/java
Enter to keep the default[*], or type selection number: 1
Using `/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre/bin/java' to provide `java'.
vi(m)
text editor
Split current vi session window vertically with FILE. Screenshot
:vspl tips.css
Split current vi session window horizontally. Screenshot
:spl
Start vi in diff mode. Screenshot
vimdiff FILE1 FILE2
Format paragraph into 79 character lines
gqap
Print the value of char under cursor in dec, hex, and oct
ga
Rot13 encode/decode current line
g?g?
When replacing accent characters or control characters, use the decimal, octal, or hex value from the "ga" command combined with CTRL+v to locate the character. These three examples replace any ö chars with unaccented 'o' chars on the current line using the decimal value, the octal value (note the 'o' modifier), and the hex value (note the 'u' modifier).
:s/CTRL+v246/o/g
:s/CTRL+vo366/o/g
:s/CTRL+vu00f6/o/g
Display a list of all accented, control, and special characters
:digraphs
Rot13 encode/decode current line
g??
w3m
a text based Web browser and pager
View URL using this text-based Web browser (tip: install w3m image helper package). Screenshot
w3m URL
Page through FILE. An alternative more or less
w3m FILE
watch
Display the output of a command repeatedly
Monitor the output of df -h every 60 seconds
watch -n 60 df -h
wc
print the number of newlines, words, and bytes in files
Count the number of words in FILE
wc -w FILE
Count the number of bytes in line
echo -n "How many bytes?" | wc -c 15
which
shows the full path of (shell) commands
Show path to COMMAND as searched for in PATH environment variable
which w3m /usr/bin/w3m
who
shows who is logged on
Show the current system runlevel (see also: runlevel)
who -r
run-level 3 Jan 15 20:45 last=S
xargs
build and execute command lines from standard input
Find regular files in current directory and subdirectories, pass the filenames to xargs to search for PATTERN
find . -type f -print0 | xargs -0 grep PATTERN
Print list of all user accounts on system, sorted alphabetically
awk -F: '{ print $1 }' /etc/passwd | sort | xargs echo
adm apache ber bin bub daemon . . . sklarm sshd sync uucp vcsa xfs
yes
output a string repeatedly until killed
Print STRING to standard output until killed or interrupted
yes STRING
Respond 'y' to all interactive questions from COMMAND
yes | COMMAND
yum
Yellowdog Updater Modified
Check for package updates on system
yum check-update
Update all packages on system
yum update
Search for packages matching NAME
yum search NAME
Clear yum cache
yum clean all
zdump
print time zone information
Print the start and end times of Daylight Saving Time for the US/Pacific time zone
zdump -v US/Pacific | grep 2008 US/Pacific Sun Mar 9 09:59:59 2008 UTC = Sun Mar 9 01:59:59 2008 PST isdst=0 US/Pacific Sun Mar 9 10:00:00 2008 UTC = Sun Mar 9 03:00:00 2008 PDT isdst=1 US/Pacific Sun Nov 2 08:59:59 2008 UTC = Sun Nov 2 01:59:59 2008 PDT isdst=1 US/Pacific Sun Nov 2 09:00:00 2008 UTC = Sun Nov 2 01:00:00 2008 PST isdst=0
Print current time for time zone
zdump US/Samoa US/Samoa Fri Dec 4 15:28:41 2009 SST
zip
package and compress (archive) files
List files contained in ZIPFILE archive
unzip -l ZIPFILE
Networking
curl
Transfer data from or to a server
Download webpage
curl https://erikberg.com <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>Erik Berg</title> <meta name="viewport" content="width=device-width, initial-scale=1"> <meta name="date" content="2004-09-28"> <meta name="revised" content="2015-10-13T16:05:10-07:00"> ... </html>
Download webpage and save it to file named stuff.html
curl -o stuff.html https://erikberg.com/api
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 23615 0 23615 0 0 173k 0 --:--:-- --:--:-- --:--:-- 173k
Same, but request that the response uses gzip compression
curl --compressed -o stuff.html https://erikberg.com/api
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 7971 0 7971 0 0 82149 0 --:--:-- --:--:-- --:--:-- 83031
Same, but suppress progress status
curl -s --compressed -o stuff.html https://erikberg.com/api
dig
DNS lookup utility
Print DNS TXT record for HOST
dig +short erikberg.com txt "v=spf1 a mx -all"
host
DNS lookup utility
Show DNS A and MX records for example.com
host example.com example.com has address 192.0.34.166
Show DNS SOA records for example.com
host -C example.com Nameserver a.iana-servers.net: example.com has SOA record dns1.icann.org. hostmaster.icann.org. 200511 1500 7200 3600 1209600 86400 Nameserver b.iana-servers.net: example.com has SOA record dns1.icann.org. hostmaster.icann.org. 200511 1500 7200 3600 1209600 86400
ip
show / manipulate routing, devices, policy routing and tunnels
Show statistics about network device wlan0
ip -s link ls wlan0
3: wlan0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
link/ether 00:90:4b:28:41:6b brd ff:ff:ff:ff:ff:ff
RX: bytes packets errors dropped overrun mcast
12242310 38660 0 0 0 0
TX: bytes packets errors dropped carrier collsns
46230383 58420 0 0 0 0
Show routing table for device eth1
ip route ls dev eth1 192.168.1.0/24 proto kernel scope link src 192.168.1.151 169.254.0.0/16 scope link default via 192.168.1.1
Show routing policy rules
ip rule ls 0: from all lookup local 32766: from all lookup main 32767: from all lookup default
Add route to 192.168.2.0/24
ip route add to 192.168.2.0/24 dev eth0
Delete route to 192.168.2.0/24
ip route del to 192.168.2.0/24 dev eth0
iptraf
mrtg
monitors traffic load on network links
Set the LANG environment variable to C and execute mrtg using the configuration set in /etc/mrtg/mrtg.cfg. This is a typical crontab entry for mrtg
env LANG=C /usr/bin/mrtg /etc/mrtg/mrtg.cfg --logging /var/log/mrtg.log
mtr
a network diagnostic tool
Display statistics for all routers packet travels through to reach HOST
mtr --interval 5 HOST
nc (netcat)
arbitrary TCP and UDP connections and listens
Issue HTTP GET request once a second to HOST on port 80 ten times (use ctrl+v + ctrl+m to insert CRLF at end of each line in HTTP request)
for ((i=1; i<=10; i++)) do netcat HOST 80 <<eof GET / HTTP/1.1 Host: Localhost eof sleep 1 done HTTP/1.1 200 OK Date: Sun, 12 Feb 2006 09:47:08 GMT Server: Apache Last-Modified: Mon, 30 Jan 2006 10:06:49 GMT ETag: "78d2b-6d4-9ae90040" Accept-Ranges: bytes Content-Length: 1748 Connection: close Content-Type: text/html; charset=UTF-8
Start netcat to listen on port 23456
netcat -l -p 23456
Connect and send FILE to HOST on port 23456
netcat HOST 23456 < FILE
netstat
print network connections, routing tables, interface statistics
Print all listening TCP servers
netstat -tln Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN tcp 0 0 :::80 :::* LISTEN tcp 0 0 :::22 :::* LISTEN tcp 0 0 :::443 :::* LISTEN
Print all listening TCP servers and the owning PID/program name (root required)
netstat -tlnp Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:587 0.0.0.0:* LISTEN 6702/sendmail tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 6702/sendmail tcp 0 0 ::1:4190 :::* LISTEN 6576/master tcp 0 0 :::143 :::* LISTEN 6576/master tcp 0 0 :::22 :::* LISTEN 6500/sshd
Print all listening UDP servers
netstat -uln Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State udp 0 0 0.0.0.0:111 0.0.0.0:* udp 0 0 192.168.1.255:123 0.0.0.0:* udp 0 0 192.168.1.154:123 0.0.0.0:* udp 0 0 127.0.0.1:123 0.0.0.0:* udp 0 0 0.0.0.0:123 0.0.0.0:* udp 0 0 :::123 :::*
Print routing table (tmtowtdi: route -en)
netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 wlan0 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 wlan0 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 wlan0
nmap
network exploration tool and security scanner
Show open ports and version information for HOST
nmap -sS -sV -O -vvv HOST
Scan 192.168.1.0 network and report what hosts respond to ICMP echo or connect requests to TCP ports 22 or 80
nmap -sP -PS22,80 192.168.1.0/24
Consult reverse DNS records for host names on NETWORK
nmap -sL NETWORK
ping
send ICMP ECHO_REQUEST to network hosts
ping HOST 100 times
ping -c 100 HOST
route
show / manipulate the IP routing table
Add default gateway 192.168.1.1 to interface eth0
route add default gw 192.168.1.1 eth0
Either of these commands delete the default gateway
route del default
route del -net 0.0.0.0
Add route to network 192.168.0.0/24 for interface eth0
route add -net 192.168.0.0 netmask 255.255.255.0 eth0
Add gateway 192.168.0.1 for 192.168.0.0 network for interface eth0
route add -net 192.168.0.0 netmask 255.255.255.0 gw 192.168.0.1 eth0
To delete the route for the 192.168.0.0 network
route del -net 192.168.0.0 netmask 255.255.255.0
scp
secure copy (remote file copy program)
Copy file foo to foobar as user eberg on host fore.ebloft.sea
scp foo eberg@fore.ebloft.sea:foobar eberg@fore's password: foo 100% 1024KB 1.0MB/s 00:01
snmpget
query SNMP entity
Print name, hardware, operating system and version information for localhost using output format -Os. See the snmpcmd manual page for a full list of output formats.
snmpget -Os -c public -v 1 localhost sysDescr.0 sysDescr.0 = STRING: Linux fore 2.6.18.8-0.7-default #1 SMP Tue Oct 2 17:21:08 UTC 2007 i686
snmpwalk
query SNMP entity and subtree
Query the system object identifer (OID) for localhost. For a list of OIDs, see /usr/share/snmp/mibs.
snmpwalk -Os -c public -v 1 localhost system sysDescr.0 = STRING: Linux fore 2.6.18.8-0.7-default #1 SMP Tue Oct 2 17:21:08 UTC 2007 i686 sysObjectID.0 = OID: netSnmpAgentOIDs.10 sysUpTimeInstance = Timeticks: (545206) 1:30:52.06 sysContact.0 = STRING: Sysadmin (root@localhost) sysName.0 = STRING: fore sysLocation.0 = STRING: Server Room ...
ss
Expanded and enhanced update to netstat
Print all listening TCP servers
ss -tln State Recv-Q Send-Q Local Address:Port Peer Address:Port LISTEN 0 128 :::22 :::* LISTEN 0 128 *:22 *:* LISTEN 0 128 127.0.0.1:5432 *:* LISTEN 0 128 ::1:5432 :::* LISTEN 0 100 ::1:25 :::* LISTEN 0 100 127.0.0.1:25 *:* LISTEN 0 100 :::443 :::* LISTEN 0 1 ::ffff:127.0.0.1:8005 :::* LISTEN 0 100 :::80 :::*
ssh
OpenSSH SSH client
Login as USER at HOST
ssh -l USER HOST
Forward local port 9999 to REMOTE_HOST port 8118. The -f option instructs SSH to run
in the background. The -N option keeps the remote SSH session open until it is
manually killed.
ssh -f -N -L 9999:REMOTE_HOST:8118 localhost
tc
show / manipulate traffic control settings
Linux traffic control engine. . .
tc -s qdisc ls dev eth0 qdisc pfifo_fast 0: bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 Sent 16381732 bytes 74313 pkt (dropped 0, overlimits 0 requeues 0) rate 0bit 0pps backlog 0b 0p requeues 0
tcpdump
dump traffic on a network
Print information about packets in even more verbose detail
tcpdump -vv
Save raw packets to FILE
tcpdump -w FILE
Print UDP packets on port 161 originating from HOST from previously saved FILE
tcpdump -r FILE udp and port 161 and src host HOST
Print packets from previously saved FILE that did not originate or terminate on the snmp (161) port
tcpdump -r FILE ! port snmp
traceroute
print the route packets take to network host
List all of the hops a packet goes through to reach HOST
traceroute HOST
whois
client for the whois service
Report owner, contact information for an IP address or domain name
whois 172.16.12.0 [Querying whois.arin.net] [whois.arin.net] OrgName: Internet Assigned Numbers Authority OrgID: IANA Address: 4676 Admiralty Way, Suite 330 City: Marina del Rey StateProv: CA PostalCode: 90292-6695 Country: US NetRange: 172.16.0.0 - 172.31.255.255 CIDR: 172.16.0.0/12 NetName: IANA-BBLK-RESERVED NetHandle: NET-172-16-0-0-1 Parent: NET-172-0-0-0-0 NetType: IANA Special Use ...
wireshark (tshark)
interactively browse network traffic (Once known as ethereal and tethereal)
Show HTTP traffic from host 192.168.1.154
tshark src host 192.168.1.154 and port http Capturing on eth1 0.000000 192.168.1.154 -> 192.168.1.151 TCP 38377 > http [SYN] Seq=4122895926 Ack=0 Win=5840 Len=0 0.001512 192.168.1.154 -> 192.168.1.151 TCP 38377 > http [ACK] Seq=4122895927 Ack=282940905 Win=1460 Len=0 0.032672 192.168.1.154 -> 192.168.1.151 TCP 38377 > http [ACK] Seq=4122895927 Ack=282940905 Win=1460 Len=0 0.033981 192.168.1.154 -> 192.168.1.151 HTTP GET / HTTP/1.1 0.100101 192.168.1.154 -> 192.168.1.151 TCP 38378 > http [SYN] Seq=4134029462 Ack=0 Win=5840 Len=0
Capture traffic on loopback device
tshark -i lo
Capture RST packets on port 6881
tshark 'port 6881 and tcp[tcpflags] & tcp-rst !=0'
Performance
free
display amount of free and used memory in the system
Report on used and available memory on the system
free
total used free shared buffers cached
Mem: 515320 507272 8048 0 14072 318448
-/+ buffers/cache: 174752 340568
Swap: 1048568 128 1048440
iostat
report CPU and input/output statistics for devices and partitions
Report disk activity statistics every five seconds for /dev/hda and its partitions
iostat -t -k -d -p /dev/hda 5 Time: 09:14:34 PM Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn hda 0.80 0.00 3.19 0 16 hda2 0.80 0.00 3.19 0 16 hda1 0.00 0.00 0.00 0 0 Time: 09:14:39 PM Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn hda 12.18 0.00 62.28 0 312 hda2 15.57 0.00 62.28 0 312 hda1 0.00 0.00 0.00 0 0 ...
top
vmstat
report virtual memory statistics
Report memory statistics every 5 seconds 12 times
vmstat 5 12 procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 0 0 128 7524 14144 318496 0 0 49 15 294 166 14 1 85 1 0 0 128 7556 14160 318500 0 0 1 133 282 83 10 0 89 1 0 0 128 7572 14160 318500 0 0 0 0 270 62 10 0 90 0 ...
Security
iptables
administration tool for IPv4 packet filtering and NAT
Print all rules, preceded by the rule number
iptables -L -n --line-numbers Chain FORWARD (policy ACCEPT) num target prot opt source destination Chain INPUT (policy ACCEPT) num target prot opt source destination 1 ACCEPT all -- 192.0.2.0/24 0.0.0.0/0 2 ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0 icmp type 8 limit: avg 1/sec burst 5 3 DROP icmp -- 0.0.0.0/0 0.0.0.0/0 icmp type 8 Chain OUTPUT (policy ACCEPT) num target prot opt source destination
Insert a rule at position two in the INPUT chain
iptables -I INPUT 2 ...
Append a rule after all of the previous ones in the INPUT chain
iptables -A INPUT ...
Delete rule number five in the INPUT chain
iptables -D INPUT 5
Delete all of the rules in the OUTPUT chain
iptables -F OUTPUT
iptables-save
save IP Tables
Save current rules to FILE in format that can be restored by iptables-restore command
iptables-save > FILE
Display all rules in IP tables with packet and byte counters
iptables-save -c # Generated by iptables-save v1.3.0 on Fri Feb 17 02:34:59 2006 *filter :FORWARD ACCEPT [0:0] :INPUT ACCEPT [34305:24343182] :OUTPUT ACCEPT [31459:4170095] [0:0] -A INPUT -s 192.0.2.0/255.255.255.0 -j ACCEPT [24:2448] -A INPUT -s 127.0.0.1 -j ACCEPT [0:0] -A INPUT -i eth0 -p icmp -m icmp --icmp-type 8 -m limit --limit 1/sec -j ACCEPT [0:0] -A INPUT -i eth0 -p icmp -m icmp --icmp-type 8 -j DROP COMMIT # Completed on Fri Feb 12 12:34:59 2006
iptables-restore
restore IP Tables
Delete any current rules and restore IP Tables from FILE created previously by the iptables-save command
iptables-restore < FILE
snort
open source network intrusion detection system
Desktop
alsamixer
soundcard mixer for ALSA soundcard driver, with ncurses interface
Manipulate sound settings for ALSA soundcard driver. Screenshot
alsamixer
display
ImageMagick's very fast image viewer
Display BMP, GIF, JPEG, PNG, SVG, PDF, TIFF FILE
display FILE
eog
GNOME's slightly slower image viewer
Display BMP, GIF, JPEG, PNG FILE
eog FILE
evince
PDF and PostScript viewer
View PDF or PostScript FILE
evince FILE
gimp
an image manipulation and paint program
Capable graphics program. See http://manual.gimp.org
inkscape
Scalable Vector Graphics (SVG) editor
Aims to compete with the likes of Adobe Illustrator and Corel Draw. Native save format is W3C standard SVG. See http://www.inkscape.org
Export existing SVGFILE to PNGFILE
inkscape --export-png=PNGFILE SVGFILE
mplayer
media player
Stream media (mpg, mov, wmv, mp3, avi, etc.) file from URL
mplayer URL
xmms
Audio player
Plays and streams MPEG, Ogg Vorbis, WAV, etc. formats
xmms
xdpyinfo
Display X Server settings
Print screen resolution and DPI
xdpyinfo | grep -C1 resolution dimensions: 1920x1200 pixels (332x210 millimeters) resolution: 147x145 dots per inch depths (7): 24, 1, 4, 8, 15, 16, 32
xset
user preference utility for X
Show X Server settings for user
xset q
Keyboard Control:
auto repeat: on key click percent: 0 LED mask: 00000000
auto repeat delay: 300 repeat rate: 62
auto repeating keys: 00ffffffdffffbbf
fadfffdfffdfe5ef
ffffffffffffffff
ffffffffffffffff
bell percent: 50 bell pitch: 400 bell duration: 100
Pointer Control:
acceleration: 5/2 threshold: 4
Screen Saver:
prefer blanking: yes allow exposures: yes
timeout: 0 cycle: 0
Colors:
default colormap: 0x20 BlackPixel: 0 WhitePixel: 16777215
Font Path:
unix/:7100
Bug Mode: compatibility mode is disabled
DPMS (Energy Star):
Standby: 7200 Suspend: 9240 Off: 14280
DPMS is Enabled
Monitor is On
File paths:
Config file: /etc/X11/xorg.conf
Modules path: /usr/X11R6/lib/modules
Log file: /var/log/Xorg.0.log
Set your friend's keyboard to repeat at three characters per second
xset r rate 250 3
Bonus: make the mouse super fast
xset m 50/2 4
After the laugh, reset mouse to the default, usually a more appropriate setting
xset m default
xwd/xwud
dump an image of an X window/image displayer
Save screen dump of display to FILE
xwd -out FILE
Display xwd screen dump from FILE
xwud -in FILE
xwininfo
shows information about window
Display size, geometry, name, color depth, etc information about selected window
xwininfo
vncserver
launches X Server for VNC
Start vncserver with desktop width and height of 1024x768 pixels
vncserver -geometry 1024x768
Stop the vncserver running on display :2
vncserver -kill :2
vncviewer
attaches to VNC server
Connect to VNC server running on HOST on display :2
vncviewer HOST:2
Bash Shell Scripting
Looping
Read input from FILE into variables name1, name2, name3
while read name1 name2 name3 do echo $name1 $name2 $name3 done < FILE
Iterate from one to ten
for (( i=1; i<=10; i++ )) do echo $i done
Another simple bash way
for i in {1..10}
do
echo $i
done
Another way to do the same thing using seq
for i in $(seq 1 10) do echo $i done
Same thing using a while loop
i=1 while (( i<=10 )) do echo $i let i+=1 done
Loop over elements in an array
ary=(foo bar baz foobar)
for ((i=0; i < ${#ary[@]}; i++))
do
echo ${ary[$i]}
done
foo
bar
baz
foobar
Loop over elements in an associative array (available in bash version 4 and later)
declare -A hash=([apple]=red [banana]=yellow [guanabana]=green)
for key in ${!hash[@]}
do
echo $key: ${hash[$key]}
done
apple: red
guanabana: green
banana: yellow
Conditionals
An if-else conditional testing two numbers for equality
if [ $foo -eq $bar ] then echo $foo equals $bar elif [ $foo -lt $bar ] then echo $foo is less than $bar elif [ $foo -gt $bar ] then echo $foo is greater than $bar fi
Another valid way to test two numbers for equality. Note: parameter expansion happens automatically within the ((expression)) construct.
if (( foo == bar )) then echo $foo equals $bar else echo $foo does not equal $bar fi
An if-else conditional testing two strings
if [ $foo = $bar ] then echo strings $foo and $bar are the same else echo strings $foo and $bar differ fi
Arithmetic Evaluation
Arithmetic expressions are evaluated inside ((expression)). If the expression evaluates to true, 1 is returned, otherwise 0. Use $((expression)) to return the result of the expression.
for i in {1..100}
do
if (( (i % (3*5)) == 0 ))
then
echo $i: FizzBuzz
fi
done
15: FizzBuzz
30: FizzBuzz
45: FizzBuzz
60: FizzBuzz
75: FizzBuzz
90: FizzBuzz
let i=2
echo $((i ** 4))
16
echo $((i > 4))
0
echo $((i < 4))
1
echo $((i == 2))
1
echo $((i += 2))
4
echo $i
4
let i=0
while ((i < 10))
do
echo $((++i))
done
1
2
3
4
5
6
7
8
9
10
Functions
store a series of commands for later execution
Save function named "psg" to search command line for first argument which is then passed to ps for output (see: pgrep)
psg () { ps uwwp $(pgrep -f ${1:?Specify a search term}) 2>/dev/null; }
psg ssh
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 2061 0.0 0.1 4568 1016 ? Ss 08:46 0:00 /usr/sbin/sshd
eb 2623 0.0 0.1 3864 688 ? Ss 08:46 0:00 /usr/bin/ssh-agent
eb 2819 0.0 0.3 4708 1820 pts/2 S+ 09:10 0:00 ssh erikberg.com
eb 2919 0.0 0.3 4540 1860 pts/6 S+ 09:25 0:00 ssh fore
Create a function named f2c to convert Fahrenheit to Celsius using the first argument to perform the conversion (see: bc)
f2c () { printf "%g\n" $(echo "(${1:?Input Missing}-32)*5/9" | /usr/bin/bc -l); }
f2c 81
27.2222
And function c2f to convert the other way
c2f () { printf "%g\n" $(echo "${1:?Input Missing}*(9/5)+32" | /usr/bin/bc -l); }
c2f 10
50
Display all defined functions. (tmtowtdi: declare -f)
typeset -f
c2f ()
{
printf "%g\n" $(echo "${1:?Input Missing}*(9/5)+32" | /usr/bin/bc -l)
}
f2c ()
{
printf "%g\n" $(echo "(${1:?Input Missing}-32)*5/9" | /usr/bin/bc -l)
}
psg ()
{
ps uwwp $(pgrep -f ${1:?Specify a search term}) 2>dev/null
}
Remove function NAME
unset -f NAME
Tips
For filenames containing spaces, rename files replacing spaces with underscores
ls 01 Don't Panic.m4a 02 Caring Is Creepy.m4a 03 In the Waiting Line.m4a 04 New Slang.m4a
for file in *[[:blank:]]*
do
mv "$file" ${file// /_}
done
ls 01_Don't_Panic.m4a 02_Caring_Is_Creepy.m4a 03_In_the_Waiting_Line.m4a 04_New_Slang.m4a
Say you have copied text with your mouse and now want to process that text further with a quick script. Saving the clipboard contents to an intermediary file or using cat is not necessary. Just use a Here Document.
while read line
do
echo processing $line
done <<eof
paste clipboard contents
eof