How can I call a function defined in a bash shell script from a C program

Question

I have

    #!/bin/sh

    func1()
    {
        echo "This is func1 from shell script"
    }

    func2()
    {
        echo "This is func2 from shell script"

    }

I want to call func1 and func2 from a C program. Can I do that ?

@abc Using and Writing Bash Dynamically Loadable Built-In Commands. You can write C code that accesses bash’s internal APIs, compile the C code into .sos, and load them into bash with the enable builtin. — andrewdotn
– andrewdotn, Commented Jan 25, 2013 at 6:27

ruakh · Accepted Answer · 2013-01-26 01:42:09Z

7

This is unlikely to be a good idea, but I suppose you could write something like this:

if (! fork()) { // TODO fork can return -1 on error; should check for that
    execl("/bin/sh", "-c", ". FILE && func1", (char *)NULL);
    // TODO should check to make sure execlp successfully replaced the process
}

where FILE is the name of the .sh file that defines func1. The above will spawn a child process, and replace that child process with an instance of Bash (or whatever your shell is) with the arguments -c (meaning "the script to run is the next argument") and . FILE && func1 (which is the script; it means "run the commands in FILE, and if that succeeds, then run the command func1").

For more information:

edited Jan 26, 2013 at 1:42

answered Jan 25, 2013 at 5:57

ruakh

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5 Comments

Ankur Agarwal Over a year ago

This also worked: system("source /home/abc/cpractice/test_functions ; func1 ; func2 "); Where is the documentation for the ; syntax used here?

ruakh Over a year ago

@abc: ; is just a way of separating commands. You can use \n instead if you prefer. (The two are not completely equivalent in all cases, but they're equivalent in most cases.)

Gordon Davisson Over a year ago

Note that if the script contains anything other than function declarations (i.e. if it's anything like a normal script), that will get executed as well. As @ruakh said, this is unlikely to be a good idea.

William Pursell Over a year ago

Probably better to use && instead of ;

ruakh Over a year ago

@WilliamPursell: Good point, thanks; I've made that change now.

zapatero · Accepted Answer · 2013-01-26 02:32:50Z

2

A little simpler than using fork / exec is the stdlib "system" command.

See man 3 system.

Assume your bash functions are in file "/tmp/scripts.sh" ...

system("bash -c \". /tmp/scripts.sh ; func1 ; func2\"");

answered Jan 26, 2013 at 2:32

zapatero

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Comments

thinkiny · Accepted Answer · 2013-01-26 02:36:05Z

0

If you want to recive the exit code of executing script, you should use system, else use vfork + exec*

answered Jan 26, 2013 at 2:36

thinkiny

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