Check shell command return value in c

Question

I want to know how can I do something like this in a C program.

if wget -q www.someurl.com;
then echo OK;
else echo Not there;
fi

Your shell snippet is hosed, you are capturing the output of wget in r, not the exit code. Anyway, the proper idiom is if wget -q www.someurl.com; then echo OK; else echo Not there; fi — tripleee
– tripleee, Commented Dec 22, 2014 at 4:14
I don't know how it is done in the shell but what I want to know is how it is done in a function in the C programming language. — user4328677
– user4328677, Commented Dec 22, 2014 at 9:05
Clearly people were able to guess what you really meant but seriously, if you post code to show what you want, you should either indicate what the problem with the code is or make sure it does what you want. — tripleee
– tripleee, Commented Dec 22, 2014 at 9:06

alk · Accepted Answer · 2014-12-21 17:12:14Z

4

From the parent do fork().
Inside the child created by 1. do exec*().
From the parent or a signal handler listening to SIGCHLD do wait(&status).
Finally use WEXITSTATUS(status) to get the equivalent to r=$? from your script.

answered Dec 21, 2014 at 14:25

alk

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2 Comments

Or use system(). You'll still need to use WEXITSTATUS to separate the return code from the signal information.

Using system() is highly unportable as one never knows which shell might get involved. @RussellReed

Hans Z. · Accepted Answer · 2014-12-21 14:27:09Z

2

I'd rather not do this through exec but through leveraging something like libcurl http://curl.haxx.se/libcurl/c/

answered Dec 21, 2014 at 14:27

Hans Z.

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