Commands tagged POSIX (9)

  • intersection between two files


    27
    grep -Fx -f file1 file2
    zarathud · 2010-05-28 14:50:14 24
  • View all date formats, Quick Reference Help Alias

    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 16
  • lines in file2 that are not in file1


    12
    grep -Fxv -f file1 file2
    zarathud · 2010-05-28 14:48:27 4
  • Makes the permissions of file2 the same as file1

    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 7
  • Grab just the title of a youtube video

    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 4
  • Display all shell functions set in the current shell environment

    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 1007
  • displays an uncluttered list of the names of all variables and functions in the current environment, (without shell functions and definitions)

    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 12
  • Print umask as letters (e.g. `rwxr-xr-x`) instead of number (e.g. `0022`)

    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


    -2
    unix-permissions convert.stat $(unix-permissions invert $(umask))
    ehmicky · 2019-02-05 14:06:08 389
  • Calculate the the last day of a month +/- from current month

    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 6

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Convert files from DOS line endings to UNIX line endings
This method will also convert mac line endings.

Fixes Centos 6.2 yum's metalink certificate errors
Fix's centos 6.2 yum's error: could not get metalink https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=x86_64 error was 14: PYCURL ERROR 77 - "Problem with the SSL CA cert (path? access rights?)" Error: Cannot retrieve metalink for repository: epel-source. Please verify its path and try again

Reducing image size
Adding the exclamation mark to the image geometry ignores the original aspect ratio. More info about image geometry: http://www.imagemagick.org/script/command-line-processing.php#geometry

Save current layout of top
'top' has fancy layout modes where you can have several windows with different things displayed. You can configure a layout and then save it with 'W'. It will then be restored every time you run top. E.g. to have two colored windows, one sorted by CPU usage, the other by memory usage, run top $ top then press the keys $ and then as you don?t want to repeat this the next time: $

Backup a file with a date-time stamp
$ buf myfile.txt This is useful when you are making small but frequent changes to a file. It keeps things organised and clear for another administrator to see what changed and at what time. An overview of changes can be deduced using a simple: $ ls -ltr

Run a script in parrallel over ssh
Runs a local script over ssh assuming ssh keys are in place. -P argument prints results to stdout. # Uses - https://code.google.com/p/parallel-ssh/

bulk rename files with sed, one-liner
Far from my favorite, but works in sh and with an old sed that doesn't support '-E'

Check SSH public and private keys matching
Tested in bash4

get you public ip address

Delete all but the latest 5 files
yes 6 (tail from 6th line)

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