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Mount a .iso file in UNIX/Linux

"-o loop" lets you use a file as a block device
This is sample output - yours may be different.
46

mount /path/to/file.iso /mnt/cdrom -oloop

nerd65536 · 2009-02-05 17:28:06 33
Remove a line in a text file. Useful to fix

In this case it's better do to use the dedicated tool
This is sample output - yours may be different.
45

ssh-keygen -R <the_offending_host>

bunam · 2010-07-11 19:37:24 16
(Debian/Ubuntu) Discover what package a file belongs to

'dpkg -S' just matches the string you supply it, so just using 'ls' as an argument matches any file from any package that has 'ls' anywhere in the filename. So usually it's a good idea to use an absolute path. You can see in the second example that 12 thousand files that are known to dpkg match the bare string 'ls'. Show Sample Output
This is sample output - yours may be different.
```
user@host:$ dpkg -S /bin/ls
coreutils: /bin/ls
user@host:$ dpkg -S ls | wc -l
12831
```
45

dpkg -S /usr/bin/ls

bwoodacre · 2009-04-18 18:18:23 25
Run a command only when load average is below a certain threshold

Good for one off jobs that you want to run at a quiet time. The default threshold is a load average of 0.8 but this can be set using atrun. Show Sample Output
This is sample output - yours may be different.
```
job 6 at 2009-02-04 19:03
```
45

echo "rm -rf /unwanted-but-large/folder" | batch

root · 2009-02-04 19:07:52 45
To print a specific line from a file

You can get one specific line during any procedure. Very interesting to be used when you know what line you want. Show Sample Output
This is sample output - yours may be different.
```
jeju:[xxx] > sed -n 5p test
line 5
jeju:[xxx] > cat test
line 1
line 2
line 3
line 4
line 5
line 6
line 7
line 8
line 9
line 10
jeju:[xxx] >
```
44

sed -n 5p <file>

Waldirio · 2009-10-15 11:00:48 140
Open Finder from the current Terminal location

I did not know this, i'd like to share...
This is sample output - yours may be different.
44

open .

vigo · 2009-06-10 10:55:20 25

List all bash shortcuts

This command shows the various shortcuts that can be use in bash, including Ctrl+L, Ctrl+R, etc... You can translate "\C-y" to Ctrl+y, for example. Show Sample Output

This is sample output - yours may be different.

abort can be found on "\C-g", "\C-x\C-g", "\e\C-g".
accept-line can be found on "\C-j", "\C-m".
alias-expand-line is not bound to any keys
arrow-key-prefix is not bound to any keys
backward-byte is not bound to any keys
backward-char can be found on "\C-b", "\eOD", "\e[D".
backward-delete-char can be found on "\C-h", "\C-?".
backward-kill-line can be found on "\C-x\C-?".
backward-kill-word can be found on "\e\C-h", "\e\C-?".
backward-word can be found on "\e\e[D", "\e[1;5D", "\e[5D", "\eb".
beginning-of-history can be found on "\e<", "\e[5~".
beginning-of-line can be found on "\C-a", "\eOH", "\e[1~", "\e[7~", "\e[H".
call-last-kbd-macro can be found on "\C-xe".
capitalize-word can be found on "\ec".
character-search can be found on "\C-]".
character-search-backward can be found on "\e\C-]".
clear-screen can be found on "\C-l".
complete can be found on "\C-i", "\e\e".
complete-command can be found on "\e!".
complete-filename can be found on "\e/".
complete-hostname can be found on "\e@".
complete-into-braces can be found on "\e{".
complete-username can be found on "\e~".
complete-variable can be found on "\e$".
copy-backward-word is not bound to any keys
copy-forward-word is not bound to any keys
copy-region-as-kill is not bound to any keys
dabbrev-expand is not bound to any keys
delete-char can be found on "\C-d", "\e[3~".
delete-char-or-list is not bound to any keys
delete-horizontal-space can be found on "\e\\".
digit-argument can be found on "\e-", "\e0", "\e1", "\e2", "\e3", ...
display-shell-version can be found on "\C-x\C-v".
do-lowercase-version can be found on "\C-xA", "\C-xB", "\C-xC", "\C-xD", "\C-xE", ...
downcase-word can be found on "\el".
dump-functions is not bound to any keys
dump-macros is not bound to any keys
dump-variables is not bound to any keys
dynamic-complete-history can be found on "\e\C-i".
edit-and-execute-command can be found on "\C-x\C-e".
emacs-editing-mode is not bound to any keys
end-kbd-macro can be found on "\C-x)".
end-of-history can be found on "\e>", "\e[6~".
end-of-line can be found on "\C-e", "\eOF", "\e[4~", "\e[8~", "\e[F".
exchange-point-and-mark can be found on "\C-x\C-x".
forward-backward-delete-char is not bound to any keys
forward-byte is not bound to any keys
forward-char can be found on "\C-f", "\eOC", "\e[C".
forward-search-history can be found on "\C-s".
forward-word can be found on "\e\e[C", "\e[1;5C", "\e[5C", "\ef".
glob-complete-word can be found on "\eg".
glob-expand-word can be found on "\C-x*".
glob-list-expansions can be found on "\C-xg".
history-and-alias-expand-line is not bound to any keys
history-expand-line can be found on "\e^".
history-search-backward is not bound to any keys
history-search-forward is not bound to any keys
insert-comment can be found on "\e#".
insert-completions can be found on "\e*".
insert-last-argument can be found on "\e.", "\e_".
kill-line can be found on "\C-k".
kill-region is not bound to any keys
kill-whole-line is not bound to any keys
kill-word can be found on "\ed".
magic-space is not bound to any keys
menu-complete is not bound to any keys
menu-complete-backward is not bound to any keys
next-history can be found on "\C-n", "\eOB", "\e[B".
non-incremental-forward-search-history can be found on "\en".
non-incremental-forward-search-history-again is not bound to any keys
non-incremental-reverse-search-history can be found on "\ep".
non-incremental-reverse-search-history-again is not bound to any keys
old-menu-complete is not bound to any keys
operate-and-get-next can be found on "\C-o".
overwrite-mode is not bound to any keys
possible-command-completions can be found on "\C-x!".
possible-completions can be found on "\e=", "\e?".
possible-filename-completions can be found on "\C-x/".
possible-hostname-completions can be found on "\C-x@".
possible-username-completions can be found on "\C-x~".
possible-variable-completions can be found on "\C-x$".
previous-history can be found on "\C-p", "\eOA", "\e[A".
quoted-insert can be found on "\C-q", "\C-v", "\e[2~".
redraw-current-line is not bound to any keys
re-read-init-file can be found on "\C-x\C-r".
reverse-search-history can be found on "\C-r".
revert-line can be found on "\e\C-r", "\er".
self-insert can be found on " ", "!", "\"", "#", "$", ...
set-mark can be found on "\C-@", "\e ".
shell-backward-kill-word is not bound to any keys
shell-backward-word is not bound to any keys
shell-expand-line can be found on "\e\C-e".
shell-forward-word is not bound to any keys
shell-kill-word is not bound to any keys
skip-csi-sequence is not bound to any keys
start-kbd-macro can be found on "\C-x(".
tab-insert is not bound to any keys
tilde-expand can be found on "\e&".
transpose-chars can be found on "\C-t".
transpose-words can be found on "\et".
tty-status is not bound to any keys
undo can be found on "\C-x\C-u", "\C-_".
universal-argument is not bound to any keys
unix-filename-rubout is not bound to any keys
unix-line-discard can be found on "\C-u".
unix-word-rubout can be found on "\C-w".
upcase-word can be found on "\eu".
vi-append-eol is not bound to any keys
vi-append-mode is not bound to any keys
vi-arg-digit is not bound to any keys
vi-back-to-indent is not bound to any keys
vi-backward-bigword is not bound to any keys
vi-backward-word is not bound to any keys
vi-bword is not bound to any keys
vi-bWord is not bound to any keys
vi-change-case is not bound to any keys
vi-change-char is not bound to any keys
vi-change-to is not bound to any keys
vi-char-search is not bound to any keys
vi-column is not bound to any keys
vi-complete is not bound to any keys
vi-delete is not bound to any keys
vi-delete-to is not bound to any keys
vi-editing-mode is not bound to any keys
vi-end-bigword is not bound to any keys
vi-end-word is not bound to any keys
vi-eof-maybe is not bound to any keys
vi-eword is not bound to any keys
vi-eWord is not bound to any keys
vi-fetch-history is not bound to any keys
vi-first-print is not bound to any keys
vi-forward-bigword is not bound to any keys
vi-forward-word is not bound to any keys
vi-fword is not bound to any keys
vi-fWord is not bound to any keys
vi-goto-mark is not bound to any keys
vi-insert-beg is not bound to any keys
vi-insertion-mode is not bound to any keys
vi-match is not bound to any keys
vi-movement-mode is not bound to any keys
vi-next-word is not bound to any keys
vi-overstrike is not bound to any keys
vi-overstrike-delete is not bound to any keys
vi-prev-word is not bound to any keys
vi-put is not bound to any keys
vi-redo is not bound to any keys
vi-replace is not bound to any keys
vi-rubout is not bound to any keys
vi-search is not bound to any keys
vi-search-again is not bound to any keys
vi-set-mark is not bound to any keys
vi-subst is not bound to any keys
vi-tilde-expand is not bound to any keys
vi-yank-arg is not bound to any keys
vi-yank-to is not bound to any keys
yank can be found on "\C-y".
yank-last-arg can be found on "\e.", "\e_".
yank-nth-arg can be found on "\e\C-y".
yank-pop can be found on "\ey".

bind -P

ricardofunke · 2012-05-28 18:51:59 16

Start COMMAND, and kill it if still running after 5 seconds
This is sample output - yours may be different.
43

timeout 5s COMMAND

kev · 2011-11-19 06:14:33 12
Attach screen over ssh

Directly attach a remote screen session (saves a useless parent bash process)
This is sample output - yours may be different.
43

ssh -t remote_host screen -r

recursiverse · 2009-07-23 06:15:04 45
Show a 4-way scrollable process tree with full details.

If you want a visual representation of the parent/child relationships between processes, this is one easy way to do it. It's useful in debugging collections of shell scripts, because it provides something like a call traceback. When a shell script breaks, just remember "awwfux".
This is sample output - yours may be different.
43

ps awwfux | less -S

ToyKeeper · 2009-07-04 09:39:28 15
RTFM function

RTFMFTW.
This is sample output - yours may be different.
42

rtfm() { help $@ || man $@ || $BROWSER "http://www.google.com/search?q=$@"; }

hunterm · 2011-01-05 02:53:38 323
Eavesdrop on your system

This command takes a snapshot of the open files for a PID 1234 then waits 10 seconds and takes another snapshot of the same PID, it then displays the difference between each snapshot to give you an insight into what the application is doing.
This is sample output - yours may be different.
42

diff <(lsof -p 1234) <(sleep 10; lsof -p 1234)

zlemini · 2010-03-15 22:55:32 13
Broadcast your shell thru ports 5000, 5001, 5002 ...

run 'nc yourip 5000', 'nc yourip 5001' or 'nc yourip 5002' elsewhere will produce an exact same mirror of your shell. This is handy when you want to show someone else some amazing stuff in your shell without giving them control over it.
This is sample output - yours may be different.
41

script -qf | tee >(nc -kl 5000) >(nc -kl 5001) >(nc -kl 5002)

clvv · 2010-10-11 07:55:30 20
What is my public IP-address?

Short command, easy to remember
This is sample output - yours may be different.
41

curl ifconfig.me

CodSpirit · 2010-08-01 13:56:01 12
Remove all files previously extracted from a tar(.gz) file.
This is sample output - yours may be different.
41

tar -tf <file.tar.gz> | xargs rm -r

prayer · 2009-07-06 22:23:11 20
which program is this port belongs to ?

Sometimes you need to use a port that is already opened by some program , and you don't know who to "kill" for it to release - so, now you do ! Show Sample Output
This is sample output - yours may be different.
```
COMMAND     PID   USER   FD   TYPE  DEVICE SIZE NODE NAME
httpd       501 apache    4u  IPv6 7656077       TCP *:http (LISTEN)
httpd       502 apache    4u  IPv6 7656077       TCP *:http (LISTEN)
httpd       503 apache    4u  IPv6 7656077       TCP *:http (LISTEN)
```
41

lsof -i tcp:80

ar_levi · 2009-04-16 14:51:53 25
directly ssh to host B that is only accessible through host A

Of course you need to be able to access host A for this ;-)
This is sample output - yours may be different.
40

ssh -t hostA ssh hostB

0x89 · 2009-08-27 21:35:19 19
Retry the previous command until it exits successfully
This is sample output - yours may be different.
39

until !!; do :; done

unixmonkey21806 · 2013-05-14 18:08:54 69
Synchronize date and time with a server over ssh

Shorter, easier to remember version of cmd#7636 NTP is better, but there are situations where it can't be used. In those cases, you can do this to sync the local time to a server. Show Sample Output
This is sample output - yours may be different.
```
Password:
Tue Aug 30 16:00:02 EDT 2011
```
39

date --set="$(ssh user@server date)"

splante · 2011-08-30 20:03:06 62
Python version 3: Serve current directory tree at http://$HOSTNAME:8000/

In Python version 3, the module was merged into http.server. Gentlemen, change your aliases. Show Sample Output
This is sample output - yours may be different.
```
$ python3.1 -m http.server
Serving HTTP on 0.0.0.0 port 8000 ...
```
39

python -m http.server

Alanceil · 2010-12-17 12:52:45 44
List only the directories

-d: list directory entries instead of contents, and do not dereference symbolic links
This is sample output - yours may be different.
39

ls -d */

brianmuckian · 2009-10-08 22:07:22 28
Edit a google doc with vim

Google just released a new commend line tool offering all sorts of new services from the commend line. One of them is uploading a youtube video but there are plenty more google services to interact with. Download it here: http://code.google.com/p/googlecl/ Manual: http://code.google.com/p/googlecl/wiki/Manual This specific command courtesy of lifehacker:http://lifehacker.com/5568817/ Though all can be found in manual page linked above. Show Sample Output
This is sample output - yours may be different.
```
Google just released a new commend line tool offering all sorts of new services from the commend line. One of them is uploading a youtube video but there are plenty more google services to interact with.
Download it here: http://code.google.com/p/googlecl/
Manual: http://code.google.com/p/googlecl/wiki/Manual
This specific command courtesy of lifehacker:http://lifehacker.com/5568817/
Though all can be found in manual page above.
```
38

google docs edit --title "To-Do List" --editor vim

spiffwalker · 2010-06-21 16:15:42 17
Run a file system check on your next boot.

The empty file /forcefsck causes the file system check fsck to be run next time you boot up, after which it will be removed. This works too: sudo >/forcefsck
This is sample output - yours may be different.
38

sudo touch /forcefsck

johnraff · 2009-10-29 17:04:47 17
Share a terminal screen with others

If you enable multiuser, then you can permit others to share your screen session. The following conditions apply: 1. screen must be suid root; 2. "multiuser on" must be configured in ~/.screenrc; 3. control the others user(s) access with "aclchg": # ----- from ~/.screenrc-users ----- aclchg someuser +rx "#?" #enable r/o access to "someuser" aclchg someuser -x "#,at,aclchg,acladd,acldel,quit" # don't allow these aclchg otheruser +rwx "#?" # enable r/w access to "otheruser" aclchg otheruser -x "#,at,aclchg,acladd,acldel,quit" # don't allow them to use these commands # ----- After doing this (once), you start your session with: $ screen Then, the other user can join your terminal session(s) with youruserid: $ screen -r youruserid/ Note: the trailing "/" is required. Multiple users can share the same screen simultaneously, each with independent access controlled precisely with "aclchg" in the ~/.screenrc file. I use the following setup: # ~/.screenrc-base # default screenrc on any host source $HOME/.screenrc-base source $HOME/.screenrc-$HOST source $HOME/.screenrc-users # ----- Then, the base configurations are in ~/.screenrc-base; the host-specific configurations are in ~/.screenrc-$HOST, and the user configurations are in ~/.screenrc-users. The host-specific .screenrc file might contain some host-specific screen commands; e.g.: # ~/.screen-myhost # ----- screen -t 'anywhere' /bin/tcsh screen -t 'anywhere1' /bin/tcsh # ---- The .screenrc-base contains: # ~/.screenrc-base ## I find typing ^a (Control-a) awkward. So I set the escape key to CTRL-j instead of a. escape ^Jj termcapinfo xterm* ti@:te@: autodetach on zombie kr verbose on multiuser on
This is sample output - yours may be different.
38

% screen -r someuser/

totoro · 2009-03-25 23:59:38 12
Google text-to-speech in mp3 format

EDIT: command updated to support accented characters! Works in any of 58 google supported languages (some sound like crap, english is the best IMO). You get a mp3 file containing your query in spoken language. There is a limit of 100 characters for the "q" parameter, so be careful. The "tl" parameter contains target language.
This is sample output - yours may be different.
37

wget -q -U Mozilla -O output.mp3 "http://translate.google.com/translate_tts?ie=UTF-8&tl=en&q=hello+world

sairon · 2011-03-08 14:05:36 23
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list all files in a directory, sorted in reverse order by modification time, use file descriptors.

It's both silly, and infinitely useful. Especially useful in logfile directories where you want to know what file is being updated while troubleshooting.

Convert seconds to [DD:][HH:]MM:SS

Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

BASH: Print shell variable into AWK

See how many more processes are allowed, awesome!

There is a limit to how many processes you can run at the same time for each user, especially with web hosts. If the maximum # of processes for your user is 200, then the following sets OPTIMUM_P to 100. $ OPTIMUM_P=$(( (`ulimit -u` - `find /proc -maxdepth 1 $ -user $USER -o -group $GROUPNAME $ -type d|wc -l`) / 2 )) This is very useful in scripts because this is such a fast low-resource-intensive (compared to ps, who, lsof, etc) way to determine how many processes are currently running for whichever user. The number of currently running processes is subtracted from the high limit setup for the account (see limits.conf, pam, initscript). An easy to understand example- this searches the current directory for shell scripts, and runs up to 100 'file' commands at the same time, greatly speeding up the command. $ find . -type f | xargs -P $OPTIMUM_P -iFNAME file FNAME | sed -n '/shell script text/p' I am using it in my http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html especially for the xargs command. Xargs has a -P option that lets you specify how many processes to run at the same time. For instance if you have 1000 urls in a text file and wanted to download all of them fast with curl, you could download 100 at a time (check ps output on a separate [pt]ty for proof) like this: $ cat url-list.txt | xargs -I '{}' -P $OPTIMUM_P curl -O '{}' I like to do things as fast as possible on my servers. I have several types of servers and hosting environments, some with very restrictive jail shells with 20processes limit, some with 200, some with 8000, so for the jailed shells my xargs -P10 would kill my shell or dump core. Using the above I can set the -P value dynamically, so xargs always works, like this. $ cat url-list.txt | xargs -I '{}' -P $OPTIMUM_P curl -O '{}' If you were building a process-killer (very common for cheap hosting) this would also be handy. Note that if you are only allowed 20 or so processes, you should just use -P1 with xargs.

Count the total number of files in each immediate subdirectory

counts the total (recursive) number of files in the immediate (depth 1) subdirectories as well as the current one and displays them sorted. Fixed, as per ashawley's comment

for too many arguments by *

$ grep ERROR *.log -bash: /bin/grep: Argument list too long $ echo *.log | xargs grep ERROR /dev/null 20090119.00011.log:DANGEROUS ERROR

get total of inodes of root partition

A signal trap that logs when your script was killed and what other processes were running at that time

trap is the bash builtin that allows you to execute commands when the current script receives a particular signal. Uses $0 for the script name, $$ for the script PID, tee to output to STDOUT as well as a log file and ps to log other running processes.

take a look to command before action

add |sh when you agree the list, I often use that method to prevent typos in dangerous or long operations

Get gzip compressed web page using wget.

Like the original command, but the -f allows this one to succeed even if the website returns uncompressed data. From gzip(1) on the -f flag: If the input data is not in a format recognized by gzip, and if the --stdout is also given, copy the input data without change to the standard output: let zcat behave as cat.

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