How to check if gcc has failed, returned a warning, or succeeded? (in bash)

Question

Hi. How would I go about checking whether gcc has succeeded in compiling a program, failed, or succeeded but with a warning?

#!/bin/sh

string=$(gcc helloworld.c -o helloworld)

if [ string -n ]; then
    echo "Failure"
else
    echo "Success!"
fi

This only checks whether it has succeeded or (failed or compiled with warnings).

-n means "is not null".

Thanks!

EDIT If it's not clear, this isn't working.

Answer 1

if gcc helloworld.c -o helloworld; then echo "Success!"; else echo "Failure"; fi

You want bash to test the return code, not the output. Your code captures stdout, but ignores the value returned by GCC (ie the value returned by main()).

Answer 2

Your condition should be:

if [ $? -ne 0 ]

GCC will return zero on success, or something else on failure. That line says "if the last command returned something other than zero."

Answer 3

To tell the difference between compiling completely cleanly and compiling with errors, first compile normally and test $?. If non-zero, compiling failed. Next, compile with the -Werror (warnings are treated as errors) option. Test $? - if 0, it compiled without warnings. If non-zero, it compiled with warnings.

Ex:

gcc -Wall -o foo foo.c
if [ $? -ne 0 ]
then
    echo "Compile failed!"
    exit 1
fi

gcc -Wall -Werror -o foo foo.c
if [ $? -ne 0 ]
then
    echo "Compile succeeded, but with warnings"
    exit 2
else
    echo "Compile succeeded without warnings"
fi