Commands using expr (16)

  • expr will give you a quick way to do basic math from the CLI. Make sure you escape things like * and leave a space between operators and digits. Show Sample Output


    4
    expr 512 \* 7
    chuckr · 2009-09-23 19:11:38 10
  • watch the seconds of your life tick away - replace YYYY-mm-dd HH:MM:ss w/ your birthtime.


    2
    while [ 0 ]; do expr 2365200000 \- `date +%s` \- `date --date "YYYY-mm-dd HH:MM:ss" +%s`; sleep 1; clear; done
    wwest4 · 2009-02-13 20:02:37 0
  • Same as original, but works in bash


    2
    while [ 1 -lt 2 ]; do i=0; COL=$((RANDOM%$(tput cols)));ROW=$((RANDOM%$(tput cols)));while [ $i -lt $COL ]; do tput cup $i $ROW;echo -e "\033[1;34m" $(cat /dev/urandom | head -1 | cut -c1-1) 2>/dev/null ; i=$(expr $i + 1); done; done
    dave1010 · 2010-05-28 16:07:56 1
  • EXAMPLES jb "next sun 12pm" "/bin/sh ~you/1.sh" & jb "2010-08-29 12:00:00" "~you/1.sh" & jb "29aug2010 gmt" ". ~you/1.sh" & jb 12:00p.m. "nohup ./1.sh" & jb 1min "echo stop!" & SEE ALSO parsedate(3) strftime(3)


    2
    jb() { if [ -z $1 ];then printf 'usage:\njb <"date and/or time"> <"commandline"> &\nsee parsedate(3) strftime(3)\n';else t1=$(date +%s); t2=$(date -d "$1" +%s) ;sleep $(expr $t2 - $t1);$2 ;fi ;}
    argv · 2010-08-26 23:50:42 0
  • Generates labyrinth-like pattern on UTF-8 terminal in bash. For fun ;) Show Sample Output


    2
    while ( true ) ; do if [ $(expr $RANDOM % 2 ) -eq 0 ] ; then echo -ne "\xE2\x95\xB1" ; else echo -ne "\xE2\x95\xB2" ; fi ; done
    tobi · 2015-01-17 12:46:37 3

  • 1
    expr `find . -type f -printf "%s + "0`
    sraeder · 2011-02-13 00:03:31 0
  • Take a screenshot every 2 seconds and save it as a png file


    1
    i=0;while :; do i=$(expr "$i" + 1); scrot "$i".png; sleep 2; done;
    scripteles · 2011-05-27 00:25:28 0
  • command was too long... this is the complete command: fname=$1; f=$( ls -la $fname ); if [ -n "$f" ]; then fsz=$( echo $f | awk '{ print $5 }' ); if [ "$fsz" -ne "0" ]; then nrrec=$( wc -l $fname | awk '{ print $1 }' ); recsz=$( expr $fsz / $nrrec ); echo "$recsz"; else echo "0"; fi else echo "file $fname does not exist" >&2; fi First the input is stored in var $fname The file is checked for existance using "ls -lart". If the output of "ls -lart" is empty, the error message is given on stderr Otherwise the filelength is taken from the output of "ls -lart" (5th field) With "wc -l" the number of records (or lines) is taken. The record size is filelength devided by the number of records. please note: this method does not take into account any headers, variable length records and only works on ascii files where the records are sperated by 0x0A (or 0x0A/0x0D on MS-DOS/Windows). Show Sample Output


    0
    fname=$1;f=$(ls -la $fname);fsz=$(echo $f|awk '{ print $5 }');nrrec=$(wc -l $fname|awk '{ print $1 }');recsz=$(expr $fsz / $nrrec);echo "$recsz"
    vuurst · 2010-09-14 08:40:22 0

  • 0
    expr `echo "123671" | sed -e 's/[0-9]/ + &/g' -e 's/^ +//g'` 20
    maher · 2012-06-24 23:12:30 0
  • Should work with sh, bash, etc. Show Sample Output


    0
    port=32768; while netstat -atn | grep -q :$port; do port=$(expr $port + 1); done; echo $port
    presto8 · 2013-08-29 17:55:55 0
  • I have this in my .bash_aliases and call it before running apt-get install or apt-get upgrade Example: alias apt-install='apt-update; apt-get install' alias apt-upgrade='apt-update; apt-get upgrade' function apt-update () { if [[ $(expr $(date +%s) - $(stat -c %X /var/lib/apt/periodic/update-success-stamp)) -gt 86400 ]]; then sudo apt-get update else echo apt is up to date fi }


    0
    if [[ $(expr $(date +%s) - $(stat -c %X /var/lib/apt/periodic/update-success-stamp)) -gt 86400 ]]; then sudo apt-get update fi
    gargolito · 2015-05-12 14:45:11 0

  • -1
    expr $(fdisk -s ` grep ' / ' /etc/mtab |cut -d " " -f1`) / 1024
    ncaio · 2009-05-21 17:25:38 2

  • -1
    dd of=output.txt if=input.txt ibs=1 skip=$(expr `stat -c%s input.txt` / 2)
    kev · 2011-07-10 12:04:48 4
  • Change HH:MM with your target time. This is for a Debian/Ubuntu GNU system. You need bash (package bash), date (package coreutils) and toilet (package toilet). Install with: # apt-get install bash coreutils toilet toilet-fonts


    -2
    watch -tn1 'date -u +%T -d @$(expr $(date -d HH:MM +%s) - $(date +%s)) | toilet -f bigmono12'
    prayer · 2010-06-26 11:56:11 0
  • plays with bash arrays. instead of storing the list of files in a temp file, this stores the list in ram, retrieves the last element in the array (the last html file), then removes it.


    -3
    a=($(ls *html)) && a=${a[$(expr ${#a[@]} - 1)]} && rm $a
    linuxrawkstar · 2009-10-12 16:40:06 2
  • Matrix Screen HPUX


    -4
    while :; do integer i=0; COL=$((RANDOM%$(tput cols))); ROW=$((RANDOM%$(tput cols))); while (( i <= COL)) do tput cup $i $ROW; echo "\033[1;34m" $(cat /dev/urandom | head -1 | cut -c1-1) 2>/dev/null; i=$(expr $i + 1); done done
    mfrancime · 2010-05-28 11:17:43 0

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Print a horizontal line

Perl one-liner to determine number of days since the Unix epoch
There are some environments that use this value for password and account expiration. It's helpful to be able to quickly determine the number of days since the Unix epoch (dse) when working directly with the configuration files as an administrator.

list directories only

Transform a portrait pdf in a landscape one with 2 pages per page
This is an example of the usage of pdfnup (you can find it in the 'pdfjam' package). With this command you can save ink/toner and paper (and thus trees!) when you print a pdf. This tools are very configurable, and you can make also 2x2, 3x2, 2x3 layouts, and more (the limit is your fantasy and the resolution of the printer :-) You must have installed pdfjam, pdflatex, and the LaTeX pdfpages package in your box.

Send your svn diff to meld
If you like to view what has been changed between revision 100 and the BASE on FILE. Meld will give you a nice overview.

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" }

reduce mp3 bitrate (and size, of course)
Useful if you have to put some mp3 files into mobile devices (ie mobile phones with no much memory)

Create a new file

history autocompletion with arrow keys
This will enable the possibility to navigate in the history of the command you type with the arrow keys, example "na" and the arrow will give all command starting by na in the history.You can add these lines to your .bashrc (without &&) to use that in your default terminal.

Synchronise a file from a remote server
You will be prompted for a password unless you have your public keys set-up.


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