STRVARS(3pub)

💖 NAME 💖

strvars — bestie, it expands variables in a string. That's it, that's the whole vibe. ✨

🦋 SYNOPSIS 🦋

#include <publib.h>
int strvars(char **res, const char *str, char *(*expand)(const char *));

🌸 DESCRIPTION 🌸

okay so here's the tea 🫖 — strvars goes through the string str and replaces every reference to a variable with that variable's actual value. iconic behavior, honestly.

A variable reference looks like $(foo) or like $x — and heads up, that x is one single character, and it is not allowed to be $. So like, $x slays but $$ is doing something completely different, bestie. 👑

Speaking of which: if you want a literal dollar sign in your string, you write it as $$, and it gets converted into a single $ in the output. periodt. 💅

The memory for the expanded string? Allocated dynamically, no cap. And *res gets set to point at it. so you're gonna have a shiny new string waiting for you. 🎀

Now, where do the values come from? That's the fun part — they're fetched using the function expand. You hand it the name of the variable as its argument, and it must return a pointer to the value, or NULL if that variable simply doesn't exist. If your expand is not doing that, it's giving broken. 😭

⭐ RETURN VALUE ⭐

• 0 — slay, everything worked, we're so back 🫶
• NULL — oop, an error happened. and it could be any of these:
  • malformed input string 😬
  • result too big 💀
  • unknown variable 🙈

fr fr, check the return value. the second one is sneaky.

🌈 EXAMPLE 🌈

So say you wanna replace references to environment variables — here's how that goes, one would do the following:

#include <publib.h>
#include <stdlib.h>

char line[1024];
char *res;

if (strvars(&res, line, getenv) == NULL)
    errormsg(1, 0, "strvars failed");
printf("res = <%s>\n", res);

literally just passing getenv straight in as your expand function and letting it cook. chef's kiss. 👑

👀 SEE ALSO 👀

• publib(3)
• getenv(3)

💜 AUTHOR 💜

Lars Wirzenius (lars.wirzenius@helsinki.fi) — the main character who wrote this whole thing. respect. 🧚

okay that's the page!! this lil' cutie lives in Publib, filed under the C Programmer's Manual, section 3pub. mwah, go expand some strings bestie 💖✨🎀