GETPROGNAME(3)

💖 GETPROGNAME(3) — the libc girlies 💅

okay so bestie, we're in the Library Functions Manual today (that's the manual name, iconic), and this page is all about getprogname, setprogname — your little program's name tag 🎀

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✨ NAME ✨

getprogname, setprogname — get or set the program name, literally that's it, that's the whole vibe 🫶

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📚 LIBRARY 📚

Standard C Library (libc, -lc) — the one you already linked, no cap 💅

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🧚 SYNOPSIS 🧚

#include <stdlib.h>

const char *
getprogname(void);

void
setprogname(const char *progname);

bestie the header is <stdlib.h> and yes you need it 💜

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🌸 DESCRIPTION 🌸

So the getprogname() and setprogname() functions manipulate the name of the current program — they're the little duo that keeps your program's identity straight ✨ They're used by error-reporting routines to produce consistent output, which is giving brand consistency, and we love that for them 👑

The getprogname() function returns the name of the program. But heads up — if the name has not been set yet, it will return NULL. 🫠 So fr fr, check before you printf("%s") it, iykyk.

The setprogname() function sets the name of the program to be the last component of the progname argument. And here's the tea 🍓 — since a pointer to the given string is kept as the program name, it should not be modified for the rest of the program's lifetime. Like, it's not a copy, it's a whole long-term relationship with your pointer, so don't be out here editing it later 🙈

In FreeBSD, the name of the program is set by the start-up code that is run before main() — so running setprogname() is not necessary there, it's already handled for you, main character energy 👑 Programs that desire maximum portability should still call it though; on another operating system, these functions may be implemented in a portability library. Calling setprogname() allows the aforementioned library to learn the program name without modifications to the start-up code. Basically: call it anyway, your future self on some other OS will thank you 💖

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🔥 EXAMPLES 🔥

The following example presents a simple program, which shows the difference between getprogname() and argv[0] — and the difference is so real, watch this:

#include <stdio.h>
#include <stdlib.h>

int
main(int argc, char** argv)
{
        printf("getprogname(): %s\n", getprogname());
        printf("argv[0]: %s\n", argv[0]);
        return (0);
}

When compiled and executed (e.g., with ./a.out) the output of the program is going to look like this:

getprogname(): a.out
argv[0]: ./a.out

see?? getprogname() gives you just a.out, but argv[0] said ./a.out with the whole path situation 💀 that's the whole point of the example bestie, the way that one has the prefix and one does not 🌈

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🦋 SEE ALSO 🦋

• err(3) — go read it, it's the friend that actually uses all this 💜
• setproctitle(3) — its sibling, different job, also slay ✨

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⭐ HISTORY ⭐

These functions first appeared in NetBSD 1.6, and made their way into FreeBSD 4.4 — glow up across operating systems, we love a journey 🌸

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💅 tiny reminder: getprogname() can hand you NULL if nothing's been set, and setprogname() keeps your pointer, not a copy. Be normal about it 🙈

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kisses bestie 💖 that was the Debian build of this page, dated April 18, 2021 — mwah, go name your program 🎀🫶