Call C function in Bash script

Question

Related to question 3451993, is it possible to call a function which is internal to subst.c (in the Bash source code) in a Bash script?

Solution 1

Bash supports loadable builtins. You might be able to make use of this to do what you want. See the files in your /usr/share/doc/bash/examples/loadables (or similar) directory.

Solution 2

It even possible to use C data structures ;)

This is ctypes.sh, a foreign function interface for bash. ctypes.sh is a bash plugin that provides a foreign function interface directly in your shell. In other words, it allows you to call routines in shared libraries from within bash.

Check out https://github.com/taviso/ctypes.sh ;)

Solution 3

The simplest way to do this is to write a simple program that collects the input, feeds it to the function, then prints the result. Why don't you tell us what you are attempting to accomplish and perhaps we can suggest an easier way to "skin this cat".

Solution 4

No.

You can't access a function internal to the shell binary from the shell if it is not exported as a shell function.

Solution 5

No, you'll have to write a short C program, compile it and call it from the shell.

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Comments

[l0b0]

I'm trying to call a function which is internal to Bash, but it looks like it's not compiled into a separate shell command. Please see the link for more info.

[Jay]

It's very difficult to do this and is usually very unreliable. You're better off trying to get what you want a different way.

[msw]

@l0b0: restating the question is not equivalent to saying what you are trying to accomplish.

[l0b0]

Good idea. Unfortunately grep subst /usr/share/doc/bash/examples/loadables/* returned nothing.

[SourceSeeker]

@l0b0: That just means you have to write your own. Also, grep subst /usr/include/bash/* gives /usr/include/bash/shell.h:#include "subst.h", grep shell.h /usr/share/doc/bash/examples/loadables/* gives a bunch. Unfortunately, grep prompt /usr/share/doc/bash/examples/loadables/* gives nothing, but grep prompt /usr/include/bash/subst.h does look interesting.

[user2284570]

The simplest way to do this is to write a simple program that collects the input, feeds it to the function, then prints the resultHow do you do this on chrome os? It is the case where all partitions are mounted with noexec except for the rootfs which is write protected.

[Jay]

Never used Chrome OS. It sounds like they don't allow you to execute anything. If that's true you won't have a simple hack. You'd probably have to write a plugin for chrome.

[mljrg]

This is the most interesting project I have seen in the past couple of years. Thanks for you answer!