execline
Software
skarnet.org

The loopwhilex program

loopwhilex performs a conditional loop.

Interface

     loopwhilex [ -n ] [ -o okcodes | -x breakcodes ] prog...

• loopwhilex runs prog... as a child process and waits for it to complete.
• As long as prog exits zero, loopwhile runs it again.
• loopwhilex then exits with an approximation of the last prog invocation's exit code.

Options

• -o okcodes : okcodes must be a comma-separated list of exit codes. loopwhilex will keep looping as long as prog exits with one of the codes in okcodes.
• -x breakcodes : like the previous option, but with inverted meaning - the listed exit codes are codes that will break the loop and exit, and the unlisted exit codes will keep the loop running.
• -n : negate the test. This option is now redundant, and may disappear soon.

Notes

• loopwhilex prog... is equivalent to loopwhilex -n -x 0 prog... and loopwhilex -o 0 prog...
• Be careful: execline maintains no state, in particular it uses no real variables, and environment will be of no use here since every instance of prog... runs as a separate child process. To avoid being stuck in an infinite loop, prog... should modify some external state - for instance, the filesystem.