Commands tagged POSIX (9)


  • 27
    grep -Fx -f file1 file2
    zarathud · 2010-05-28 14:50:14 4
  • If you have used bash for any scripting, you've used the date command alot. It's perfect for using as a way to create filename's dynamically within aliases,functions, and commands like below.. This is actually an update to my first alias, since a few commenters (below) had good observations on what was wrong with my first command. # creating a date-based ssh-key for askapache.github.com ssh-keygen -f ~/.ssh/`date +git-$USER@$HOSTNAME-%m-%d-%g` -C 'webmaster@askapache.com' # /home/gpl/.ssh/git-gplnet@askapache.github.com-04-22-10 # create a tar+gzip backup of the current directory tar -czf $(date +$HOME/.backups/%m-%d-%g-%R-`sed -u 's/\//#/g' <<< $PWD`.tgz) . # tar -czf /home/gpl/.backups/04-22-10-01:13-#home#gpl#.rr#src.tgz . I personally find myself having to reference date --help quite a bit as a result. So this nice alias saves me a lot of time. This is one bdash mofo. Works in sh and bash (posix), but will likely need to be changed for other shells due to the parameter substitution going on.. Just extend the sed command, I prefer sed to pretty much everything anyways.. but it's always preferable to put in the extra effort to go for as much builtin use as you can. Otherwise it's not a top one-liner, it's a lazyboy recliner. Here's the old version: alias dateh='date --help|sed "/^ *%%/,/^ *%Z/!d;s/ \+/ /g"|while read l;do date "+ %${l/% */}_${l/% */}_${l#* }";done|column -s_ -t' This trick from my [ http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html bash_profile ] Show Sample Output


    21
    alias dateh='date --help|sed -n "/^ *%%/,/^ *%Z/p"|while read l;do F=${l/% */}; date +%$F:"|'"'"'${F//%n/ }'"'"'|${l#* }";done|sed "s/\ *|\ */|/g" |column -s "|" -t'
    AskApache · 2010-04-21 01:22:18 5

  • 11
    grep -Fxv -f file1 file2
    zarathud · 2010-05-28 14:48:27 0
  • same as the chmod example, but should also copy extended access control list attributes. deliberately stolen from: man setfacl


    6
    getfacl file1 | setfacl --set-file=- file2
    funky · 2010-03-31 13:36:53 2
  • There's another version on here that uses GET but some people don't have lwp-request, so here's an alternative. It's also a little shorter and should work with most youtube URLs since it truncates at the first &


    2
    url="[Youtube URL]"; echo $(curl ${url%&*} 2>&1 | grep -iA2 '<title>' | grep '-') | sed 's/^- //'
    rkulla · 2010-04-29 02:03:36 1
  • Uses the shell builtin `declare` with the '-f' flag to output only functions to grep out only the function names. You can use it as an alias or function like so: alias shfunctions="builtin declare -f | command grep --color=never -E '^[a-zA-Z_]+\ \(\)'" shfunctions () { builtin declare -f | command grep --color=never -E '^[a-zA-Z_]+\ \(\)'; } Show Sample Output


    2
    builtin declare -f | command grep --color=never -E '^[a-zA-Z_]+\ \(\)'
    sciro · 2018-07-23 05:24:04 0
  • Normally executing 'set' returns a vast amount of information, including the source code of every function and variable within the environment - including those that are part of the shell. By using the -o posix argument, bash runs temporarily in POSIX mode for this command, which simplifies expressions and leaves out the shell's own functions and definitions - leaving a much smaller, more useful list. Show Sample Output


    0
    alias allvars=' ( set -o posix; set ) | less'
    incidentnormal · 2016-03-04 14:04:45 0
  • Install with `npm install unix-permissions`. https://github.com/ehmicky/unix-permissions Unix file permissions can take many shapes: symbolic (`ug+rw`), octal (`660`) or a list of characters (`drw-rw----`). `unix-permissions` enables using any of these (instead of being limited to a single one) with any CLI command. Show Sample Output


    -1
    unix-permissions convert.stat $(unix-permissions invert $(umask))
    ehmicky · 2019-02-05 14:06:08 0
  • This produces a parseable output of the last day of the month in future or past. Change the '-v-0m' to be a month plus or minus from the current system time. Show Sample Output


    -4
    date -j -v1d -v-0m -v-1d +'%m %d %Y'
    drewk · 2010-03-04 17:47:51 1

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zgrep across multiple files

A nice command for summarising repeated information

Find usb device in realtime
Using this command you can track a moment when usb device was attached.

Remove a file whose name begins with a dash ( - ) character
Using the redundant ./ directory information prevents the dash from occurring at the beginning of the filename, and being interpreted as an option of the rm command. Also works using: $ rm -- -filename

Multi-thread any command
For instance: $ find . -type f -name '*.wav' -print0 |xargs -0 -P 3 -n 1 flac -V8 will encode all .wav files into FLAC in parallel. Explanation of xargs flags: -P [max-procs]: Max number of invocations to run at once. Set to 0 to run all at once [potentially dangerous re: excessive RAM usage]. -n [max-args]: Max number of arguments from the list to send to each invocation. -0: Stdin is a null-terminated list. I use xargs to build parallel-processing frameworks into my scripts like the one here: http://pastebin.com/1GvcifYa

identify exported sonames in a path
This provides a list of shared object names (sonames) that are exported by a given tree. This is usually useful to make sure that a given required dependency (NEEDED entry) is present in a firmware image tree. The shorter (usable) version for it would be $ scanelf -RBSq -F "+S#f" But I used the verbose parameters in the command above, for explanation.

Set laptop display brightness
Run as root. Path may vary depending on laptop model and video card (this was tested on an Acer laptop with ATI HD3200 video). $ cat /proc/acpi/video/VGA/LCD/brightness to discover the possible values for your display.

Lists all usernames in alphabetical order
Save some CPU, and some PIDs. :)

Play music from youtube without download
same as above but dumps the stream to a file.

GRUB2: set Super Mario as startup tune
I'll let Slayer handle that. Raining Blood for your pleasure.


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