wiki.bash-hackers.org/syntax/ccmd/while_loop.md

====== The while-loop ======

===== Synopsis =====
<code>
while <LIST1> ; do
  <LIST2>
done
</code>

===== Description =====
The while-loop is relatively simple in what it does: it executes the [[syntax:basicgrammar#lists | command list]] ''<LIST1>'' and if the exit code of it was 0 (TRUE) it executes ''<LIST2>''. This happens again and again until ''<LIST1>'' returns FALSE.

This is exactly the opposite of the [[syntax:ccmd:until_loop | until loop]].

:!: Like all loops (both ''for''-loops, ''while'' and ''until''), this loop can be
  * terminated (broken) by the ''break'' command, optionally as ''break N'' to break ''N'' levels of nested loops
  * forced to immediately do the next iteration using the ''continue'' command, optionally as ''continue N'' analog to ''break N''

==== Return status ====

The return status is the one of the last command executed in ''<LIST2>'', or ''0'' (''TRUE'') if none was executed.

===== Examples =====


===== Portability considerations =====


===== See also =====

  * Internal: [[syntax:ccmd:until_loop | The until loop]]
  * Internal: [[commands:builtin:read#code_examples|code examples of the read builtin command]] to see how you can loop over lines