Bash while loops are pretty readable and the above would be a nice to iterate over lines if it wasn't for that gnarly pipe, which is a common source of errors in this construct. Remember that a pipe starts a new shell. So:

  grep stuff file.txt | while read key value ; do [ "$key" = "target" ] && found="$value" ; done

where you might expect $found to end up with the value for the line that has "target" in the first column. Then you notice that darn pipe symbol. The variable found is set in a subshell that terminates and the value is lost. This is a problem every time you need to keep some sort of state when looping. If you can tolate a bash-ism then you could do:

  while read key value ; do [ "$key" = "target" ] && found="$value" ; done < <(grep stuff file.txt)

but that doesn't read as nice and isn't compatible. It does avoid a common source of problems though, and might be worth getting into muscle memory for the times it is needed.

▲ eqvinox 10 hours ago | parent | next [-]

You can put the "< <( foo )" before the "while" btw, for pipe-like ordering of things. All redirections can be anywhere on the command line.

▲ dylan604 14 hours ago | parent | prev [-]

> and isn't compatible

is that a GNU v POSIX type of compatibility issue?

	▲	eqvinox 10 hours ago \| parent [-]
		bash vs. POSIX sh (or some other shells) zsh should be bash compatible on this AFAIR