Commands tagged substitution (19)

  • 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 ssh-keygen -f ~/.ssh/`date +git-$USER@$HOSTNAME-%m-%d-%g` -C '' # /home/gpl/.ssh/ # 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 [ bash_profile ] Show Sample Output

    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
  • Define a function vert () { echo $1 | grep -o '.'; } Use it to print some column headers paste <(vert several) <(vert parallel) <(vert vertical) <(vert "lines of") <(vert "text can") <(vert "be used") <(vert "for labels") <(vert "for columns") <(vert "of numbers") Show Sample Output

    echo "vertical text" | grep -o '.'
    dennisw · 2009-09-11 03:45:04 1
  • The above is just a prove of concept based around the nested bash substitution. This could be useful in situations where you're in a directory with many filetypes but you only want to convert a few. for f in *.bmp *.jpg *.tga; do convert $f ${f%.*}.png; done or you can use ls | egrep to get more specific... but be warned, files with spaces will cause a ruckus with expansion but the bash for loop uses a space delimited list. for f in $(ls | egrep "bmp$|jpg$|tga$"); do convert $f ${f%.*}.png; done I'm guessing some people will still prefer doing it the sed way but I thought the concept of this one was pretty neat. It will help me remember bash substitutions a little better :-P Show Sample Output

    for f in t1.bmp t2.jpg t3.tga; do echo ${f%.*}.png; done
    zed · 2010-07-09 00:38:53 0
  • A bitcoin "brainwallet" is a secret passphrase you carry in the "wallet" of your brain. The Bitcoin Brainwallet Private Key Calculator calculates the standard base58 encoded bitcoin private key from your "brainwallet" passphrase. The private key is the most important bitcoin number. All other numbers can be derived from it. This command uses 3 other functions - all 3 are defined on my user page: 1) brainwallet_exponent() - search for Bitcoin Brainwallet Exponent Calculator 2) brainwallet_checksum() - search for Bitcoin Brainwallet Exponent Calculator 3) b58encode() - search for Bitcoin Brainwallet Base58 Encoder Do make sure you use really strong, unpredictable passphrases (30+ characters)! can be used to check the accuracy of this calculator. Show Sample Output

    (read -r passphrase; b58encode 80$( brainwallet_exponent "$passphrase" )$( brainwallet_checksum "$passphrase" ))
    nixnax · 2014-02-18 02:50:09 1
  • In this simple example the command will add a comma to the end of every line except the last. I found this really useful when programatically constructing sql scripts. See sample output for example. Show Sample Output

    sed -e "$ ! s/$/,/"
    jgc · 2009-10-13 10:13:52 1
  • A bitcoin "brainwallet" is a secret passphrase you carry in your brain. The Bitcoin Brainwallet Exponent Calculator is one of three functions needed to calculate the bitcoin PRIVATE key. Roughly, the formula is exponent = sha256 (passphrase) Note that this is a bash function, which means you have to type its name to invoke it. You can check the accuracy of the results here Show Sample Output

    function brainwallet_exponent () { printf %s "$1"|sha256sum|head -c 64; }
    nixnax · 2014-02-18 01:49:09 1
  • A bitcoin "brainwallet" is a secret passphrase you carry in your brain. The Bitcoin Brainwallet Exponent Calculator is the second of three functions needed to calculate a bitcoin PRIVATE key. Roughly, checksum is the first 8 hex digits of sha256(sha256(0x80+sha256(passphrase))) Note that this is a bash function, which means you have to type its name to invoke it Show Sample Output

    function brainwallet_checksum () { (o='openssl sha256 -binary'; p='printf';($p %b "\x80";$p %s "$1"|$o)|$o|sha256sum|cut -b1-8); }
    nixnax · 2014-02-18 02:07:02 2

  • 4
    awk '{print $1}' < three-column.txt > first-column.txt
    infinull · 2010-07-09 04:00:05 0
  • There is a common command for outputting a field or list of fields from each line in a file. Why wouldn't you just use cut?

    cut -f 1 three-column.txt > first-column.txt
    postrational · 2010-07-11 10:13:45 1
  • Like 7171, but fixed typo, uses fewer variables, and even more cryptic! Show Sample Output

    read -a A<<<".*.**..*....*** 8 9 5 10 6 0 2 11 7 4";for C in `date +"%H%M"|fold -w1`;do echo "${A:${A[C+1]}:4}";done
    __ · 2010-12-02 22:04:49 1

  • 3
    echo "vertical text" | fold -1
    zude · 2009-10-05 23:20:14 0
  • cryptic version Show Sample Output

    read -a A <<<"8 9 5 10 6 0 3 11 7 4";B='.*.**..*....***';for C in $(date +"%H%M"|fold -w1);do echo "${B:${A[C]}:4}";done
    unefunge · 2010-11-26 11:29:23 2
  • The above is an example of grabbing only the first column. You can define the start and end points specifically by chacater position using the following command: while read l; do echo ${l:10:40}; done < three-column-list.txt > column-c10-c40.txt Of course, it doesn't have to be a column, or extraction, it can be replacement while read l; do echo ${l/foo/bar}; done < list-with-foo.txt > list-with-bar.txt Read more about parameter expansion here: Think of this as an alternative to awk or sed for file operations

    while read l; do echo ${l%% *}; done < three-column-list.txt > only-first-column.txt
    zed · 2010-07-09 03:42:56 0
  • eg: Already running cmd sleep 120 Substitution cmd c=$(pgrep sleep) && sleep 5 && kill $c

    c=$(pgrep <cmd>) && <new_cmd> && kill $c
    totti · 2011-09-14 19:58:30 0
  • See "Parameter Expansion" in the bash manpage. They refer to this as "Use Alternate Value", but we're including the var in the at alternative. Show Sample Output

    command ${MYVAR:+--someoption=$MYVAR}
    pdxdoughnut · 2015-11-04 19:47:24 0
  • If you want all the URLs from all the sessions, you can use : perl -lne 'print for /url":"\K[^"]+/g' ~/.mozilla/firefox/*/sessionstore.js Thanks to tybalt89 ( idea of the "for" statement ). For perl purists, there's JSON and File::Slurp modules, buts that's not installed by default.

    perl -lne 'print for /url":"\K[^"]+/g' $(ls -t ~/.mozilla/firefox/*/sessionstore.js | sed q)
    sputnick · 2009-12-14 00:51:54 0

  • 0
    $ bitgen hex 12312381273918273128937128912c3b1293cb712938cb12983cb192cb1289b3 info
    Label10 · 2019-03-27 21:25:29 2

  • 0
    (read -r passphrase; b58encode 80$( brainwallet_exponent "$passphrase" )$( brainwallet_checksum "$passphrase" ))
    Jacki188 · 2019-09-15 21:31:52 5

  • -5
    while read col1 col23; do echo $col1; done < three-column.txt > first-column.txt
    infinull · 2010-07-09 03:59:20 0

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Check if the Debian package was used since its installation/upgrade.
This script compares the modification date of /var/lib/dpkg/info/${package}.list and all the files mentioned there. It could be wrong on noatime partitions. Here is non-oneliner: #!/bin/sh package=$1; list=/var/lib/dpkg/info/${package}.list; inst=$(stat "$list" -c %X); cat $list | ( while read file; do if [ -f "$file" ]; then acc=$(stat "$file" -c %X); if [ $inst -lt $acc ]; then echo used $file exit 0 fi; fi; done exit 1 )

Deleting Files from svn which are missing

Convert unix timestamp to date

Reuse all parameter of the previous command line
!* is all of the arguments to the previous command rather than just the last one. This is useful in many situations. Here's a simple example: $ vi cd /stuff oops! [exit vi, twice] $ !* expands to: cd /stuff

Speaking alarm clock
This ran on a ubuntu box using espeak for speaking text with the bash shell. On a mac you should use 'say'. Also you can change your alarm interval and your snooze interval which are currently 8 hours and 1 minute. I would run this via cron yet it's easier to disable if you run it as a command like this :P

Add the time to BASH prompt
Adds the time in 12hr AM/PM format to the beginning of a prompt. Change \@ to \t for 24-hour time or \T for 12hr without AM/PM. To keep the time the next time you open a terminal, edit ~/.bashrc and stick the command at the bottom.

Use tagged vlans
Great for sysadmins! Don't forget to pass the vlan to your port in a manageable switch. After vconfig, you should use $sudo ifconfig eth0.[VID] up Now the interface is up, you can use dhclient or ifconfig again to get an ip address.

Kill a process by its partial name (BSD/Mac)
This kills Activity Monitor

To have only unique lines in a file

Change Random Wallpaper on Gnome 3
Change Random Wallpaper on Gnome 3

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