How to run C functions in shell?

Question

While learning C, I've recognized that you can see the manual of its functions within linux shell (I've been using BASH). For example:

man strlen
man crypt
man printf

I'd figured that maybe I could use those functions in shell scripting.

Is this true? How can I use those functions in shell script?

Answer 1

You can't. Manpages are a relic of a time when there were no IDEs, and no Web to look things up in. You would write your code in an editor such as ed or vim or emacs , look up functions with man , compile with cc . The fact that man command looks up C functions does not mean you get to use those functions directly in a shell.

However, some of those functions also have an equivalent in *NIX: man 3 printf is a C function, but man 1 printf is a *NIX one.

Answer 2

The short answer is, you can't use functions from the C library directly in the shell.

Look at the different man pages you get with the following commands:

man 1 printf
man 3 printf

The first one comes from section 1 (user commands), and the second one comes from section 3 (C library). While they serve a similar purpose, they are not the same. You can use the printf described in section 1 directly in the shell. Check out man 7 man to see a list of different sections.