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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Rename files in batch

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

grep lines containing two consecutive hyphens

Copy files from multiple directories into one directory

View internet connection activity in a browser
The output of lsof is piped to txt2html which converts it to html. # Perl module HTML::TextToHTML needed

a function to create a box of '=' characters around a given string.
First argument: string to put a box around. Second argument: character to use for box (default is '=') Same as command #4948, but shorter, and without the utility function.

list block devices
Shows all block devices in a tree with descruptions of what they are.

Function to check whether a regular file ends with a newline
tail -c 1 "$1" returns the last byte in the file. Command substitution deletes any trailing newlines, so if the file ended in a newline $(tail -c 1 "$1") is now empty, and the -z test succeeds. However, $a will also be empty for an empty file, so we add -s "$1" to check that the file has a size greater than zero. Finally, -f "$1" checks that the file is a regular file -- not a directory or a socket, etc.

Colorized grep in less
Get your colorized grep output in less(1). This involves two things: forcing grep to output colors even though it's not going to a terminal and telling less to handle those properly.

Get a list of IP Addresses that have failed to login via SSH
This command shows a sorted list of the IP addresses from which there have been authentication errors via SSH (possible script kiddies trying to gain access to your server), it eliminates duplicates so it's easier to read, but you can remove the "uniq" command at the end, or even do a "uniq -c" to have a count of how many times each IP address shows in the log (the path to the log may vary from system to system)


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