Grep exit codes in Makefile
exit-code, grep, makefile
Solution
The separate lines of a series of actions in a `makefile` are normally executed in separate sub-shells. To code what you're after, then:
all:
if grep term log*; \
then echo found; \
else echo not found; \
fi
That's a single command; it tests the exit status of `grep` directly. Note the liberal use of semi-colons; that's necessary because it all gets flattened when passed to the shell. Note too that the `-` is not needed; the statement as a whole exits with status 0 because one of the `echo` commands is executed, succeeds, and that is the status returned from the sub-shell. But there's another part to the trick; IIRC, the script is invoked with `/bin/sh -e` so the script exits on the first error (non-zero) status from a shell command — except in explicit conditionals such as an `if`.
If you want to explicitly capture the status of `grep` (if only to be sure it's being done right), then:
all:
-grep term log*; \
status=$$?; echo $$status; \
if [ $$status = 0 ]; \
then echo found; \
else echo not found; \
fi
You probably need the `-` this time because the `grep` is not executed as part of a shell conditional and a non-zero exit status could trigger the `-e` processing. I don't recommend futzing with this.
You might note that you can do `cd` commands in an action and because each action is executed separately, you have to do it repeatedly.
install: ${PROG}
cd ${INSTBIN}; ${RM_F} ${PROG}
${CP} ${PROG} ${INSTBIN}
cd ${INSTBIN}; ${CHOWN} ${OWNER}:${GROUP} ${PROG}; ${CHMOD} ${PERMS} ${PROG}
Yes, you can do it differently — I'm demonstrating a point, not advocating a style of installing programs.
Problem
I would like to check the result of a grep search in a Makefile. Contrary to this solution, I do not wish to use the shell command. Also, I don't want the Makefile to raise an error when grep do not find the string (exit code of 1 is treated as an error). The following tries to ignore the error and check the exit code : ``` all: -grep term log* echo $$? @case "$$?" in \ 0)\ echo "found";; \ *) \ echo "not found";;\ esac; ``` Unfortunately, the exit code is always 0.