NAME
       loop - syntactic sugar for commandline loops


SYNOPSIS
       loop [-cfhrvw] [-d seconds] [-i iterations] command


DESCRIPTION
       The  loop  utility  eases  the creation of common commandline loops one
       would usually build upon while or  for.   It's  primarily  designed  to
       reduce the number of keystrokes during a shell session.


OPTIONS
       -c, -C Enables (-c) or disables (-C) clear(1) mode, where the screen is
              cleared every single iteration, before the command is executed.

       -d seconds, -D
              Enables or disables delay mode. In this mode, after each  execu‐
              tion  of  command,  the script is paused for the given number of
              seconds.

       -f, -F Enables or disables failure ignore mode. In this mode, the  loop
              will continue even if the command exits with a failure status.

       -h, -H Print a short help message on STDOUT or STDERR and exit.

       -i iterations, -I
              Enables or disables iteration limit mode. In this mode, the loop
              will be aborted after the given number of  iterations  -  unless
              another break condition has occured before.

       -r, -R Enables  or  disables readline mode. In this mode, the loop will
              invoke the read(1) command for every iteration  and  export  the
              content  in the $LINE environment variable. Execution is stopped
              as soon as EOF is encountered.

       -v, -V Enables or disables verbose mode.

       -w, -W Enables or disables waitkey mode, where the loop is paused after
              each iteration until the RETURN key is pressed.


COMMANDS
       The  command  may  be any shell command applicable. One should note the
       common pitfalls with shell escaping, such as the fact that the exported
       $LINE  and  $ITER  variables have to be escaped and, e.g., stream redi‐
       rection can get a bit tricky. The easiest way to  get  around  this  is
       usually to simply put the command in quotes.


EXAMPLES
       # Print "Hello World!" twice
       loop -i 2 echo Hello World!

       # Clear screen, run phpunit(1), ignore failures but do not start over
       # until RETURN is pressed
       loop -fc phpunit --wait --colors MyTestCase.php

       # Display the source of loop(1), one line per second, enumerated
       loop -rd 1 'echo "`printf %3d $ITER` $LINE"' < `which loop`


ENVIRONMENT VARIABLES
       The  loop  utility  does  not need any setup. However, it's possible to
       assign a default for the most common options:

       LOOP_CLEAR
              Corresponds to the -c option;  if  nonempty,  loop  will  be  in
              clear(1) mode by default. Can be overridden with -C.

       LOOP_IGNORE_FAILURES
              Corresponds  to  the  -f  option;  if nonempty, loop will ignore
              failures by default. Can be overridden with -F.

       LOOP_VERBOSE
              Corresponds to the -v option; if nonempty, loop will create ver‐
              bose output by default. Can be overriden with -V.

       LOOP_WAITKEY
              Corresponds  to  the  -w option; if nonempty, loop will wait for
              keystrokes by default. Can be overridden with -W.


BUGS
       Probably infinite. Especially the 'wait' mode, which is currently based
       on dd(1) and stty(1), may not be that portable.


SEE ALSO
       clear(1), getopt(1), sh(1)


COPYING
       Mathias  J.  Hennig  wrote this script and it's manual page. As long as
       you retain this notice you can do whatever you want  with  this  stuff.
       If  we meet some day, and you think this stuff is worth it, you can buy
       me a beer in return.