for i in a b c; do
echo hi | grep -q bye | break
done
for i in a b c; do
echo hi | grep -q bye || break
done
The most common cause of this issue is probably using a single
|
when ||
was intended. The reason this
message appears, though, is that a construction like this, intended to
surface a failure inside of a loop:
for i in a b c; do false | break; done; echo ${PIPESTATUS[@]}
may appear to work:
$ for i in a b c; do false | break; done; echo ${PIPESTATUS[@]}
1 0
What's actually happening, though, becomes clear if we add some
echo
s; the entire loop completes, and the
break
has no effect.
$ for i in a b c; do echo $i; false | break; done; echo ${PIPESTATUS[@]}
a
b
c
1 0
$ for i in a b c; do false | break; echo $i; done; echo ${PIPESTATUS[@]}
a
b
c
0
Because bash processes pipelines by creating subshells, control
statements like break
only take effect in the subshell.
Contrast with the related, but different, problem in this link.
Bash Reference Manual: Pipelines, esp.:
Each command in a pipeline is executed in its own subshell.
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.