How do I achieve tilde expansion in C?

Question

chdir("~/") doesn't seem to work. Am I expected to look at the string and substitute tilde by hand, or is there some better way?

I want to say that is built in to a shell. Shouldn't be to difficult to roll your own. — squiguy, Apr 13 '13 at 18:21

score 18 · Accepted Answer · answered Apr 13 '13 at 18:27

18

POSIX provides wordexp(3) to perform shell-like expansion, including tilde expansion.

answered Apr 13 '13 at 18:27

Cairnarvon

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score 18 · Answer 2 · answered Apr 13 '13 at 18:28

18

You can you use wordexp example below

#include <stdio.h>
#include <wordexp.h>

int main(int argc, char* argv[]) {
    wordexp_t exp_result;
    wordexp(argv[1], &exp_result, 0);
    printf("%s\n", exp_result.we_wordv[0]);
}

answered Apr 13 '13 at 18:28

FDinoff

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7

If you use this in a function, you'll want to add `wordfree(&exp_result);` to avoid leaking memory. – ishmael Jan 11 '17 at 05:09

score 8 · Answer 3 · answered Apr 13 '13 at 18:21

The tilde in a path is a shell specific thing. What you can do see if the first character is a tilde and a slash (or a tilde end end of the string), then replace the tilde with the value of the environment variable HOME (which you can get from getenv).

If the second character is not a slash, it's most likely in the form of ~user/path. Then you have to extract the user-name and use e.g. getpwnam to get the password entry of the user, which contains that users home directory.

How do I achieve tilde expansion in C?

3 Answers3

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