Linux Shell Scripting Cookbook, Second Edition - Second Edition

Running a command until it succeeds

When using your shell for everyday tasks, there will be cases where a command might succeed only after some conditions are met, or the operation depends on an external event (such as a file being available to download). In such cases, one might want to run a command repeatedly until it succeeds.

How to do it...

Define a function in the following way:

repeat()
{
  while true
  do
    $@ && return
  done
}

Or, add this to your shell's rc file for ease of use:

repeat() { while true; do $@ && return; done }

How it works...

We create a function called repeat that has an infinite while loop, which attempts to run the command passed as a parameter (accessed by $@) to the function. It then returns if the command was successful, thereby ...