Commands using expr (16)

  • Quick command line math

    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 20
  • Mortality Countdown

    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 22
  • Blue Matrix

    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 5
  • "at" command w/o the resource usage/competition issues

    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 3
  • Labyrinth pattern

    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 10
  • Sum file sizes


    1
    expr `find . -type f -printf "%s + "0`
    sraeder · 2011-02-13 00:03:31 4
  • Take a screenshot every 2 seconds

    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 3
  • give record size of given record-structured file

    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 3
  • a simple way to calculate the sum of all digits of a number


    0
    expr `echo "123671" | sed -e 's/[0-9]/ + &/g' -e 's/^ +//g'` 20
    maher · 2012-06-24 23:12:30 3
  • find an unused unprivileged TCP port

    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 8
  • debian based OS update apt/dpkg only if it hasn't been updated in N time

    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 10
  • Alternative way to get the root directory size in megabytes


    -1
    expr $(fdisk -s ` grep ' / ' /etc/mtab |cut -d " " -f1`) / 1024
    ncaio · 2009-05-21 17:25:38 6
  • truncate half of `input.txt`


    -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 7
  • big countdown clock with hours, minutes and seconds

    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 3
  • remove the last of all html files in a directory

    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 5
  • Blue Matrix

    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 3

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scping files with streamlines compression (tar gzip)
it compresses the files and folders to stdout, secure copies it to the server's stdin and runs tar there to extract the input and output to whatever destination using -C. if you emit "-C /destination", it will extract it to the home folder of the user, much like `scp file user@server:`. the "v" in the tar command can be removed for no verbosity.

pipe output to notify-send
Route output to notify-send to show nice messages on the desktop, e.g. title and interpreter of the current radio stream

bash: display disks by id, UUID and HW path
Shows a tree of the disks. Requires "tree"

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

A command's package details
In Debian based distros, this command will list 'binutils' package details which contains 'nm' command. You can replace 'nm' to any other command.

locate bin, src, and man file for a command

Get max number of arguments
Get max number of arguments that can be accepted by the exec() system call.

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

Arch Linux sort installed packages by size
This one-liner will output installed packages sorted by size in Kilobytes.

Get a list of the top 10 heaviest tables in your mysql database - useful for performance diagnostics

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