getpass(3)

💖 getpass(3) — the "get a password" function, Library Functions Manual 💖

okay bestie, sit down, because we're about to talk about getpass, an icon of the Library Functions Manual who is, and I cannot stress this enough, fully obsolete. She's giving vintage. She's giving "please do not." Let's get into it 🎀

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✨ NAME ✨

getpass — get a password 👀🔑

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🌸 LIBRARY 🌸

Standard C library (libc, -lc)

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🦋 SYNOPSIS 🦋

#include <unistd.h>

[[deprecated]] char *getpass(const char *prompt);

🧚 Feature Test Macro Requirements for glibc

(go peek at feature_test_macros(7) if you need the lore)

getpass():
    Since glibc 2.2.2:
        _XOPEN_SOURCE && ! (_POSIX_C_SOURCE >= 200112L)
            || /* glibc >= 2.19: */ _DEFAULT_SOURCE
            || /* glibc <= 2.19: */ _BSD_SOURCE
    Before glibc 2.2.2:
        none

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💅 DESCRIPTION 💅

Okay so. This function is obsolete. Do not use it. Not even being dramatic, that's literally what the docs say. Go read NOTES below, I promise it's worth it. And if what you actually want is to read input with terminal echoing turned off, go look at the description of the ECHO flag in termios(3type) instead, bestie, that's the move 🫶

So what does getpass() even do? It:

• opens /dev/tty (that's the controlling terminal of the process, the way your program's terminal-y home base) 🏠
• outputs the string prompt
• turns off echoing (so nobody sees you typing, iconic)
• reads one line — the "<password>" if you will ✨
• restores the terminal state
• and closes /dev/tty again

that's the whole routine. periodt.

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👑 RETURN VALUE 👑

getpass() hands you back a pointer to a static buffer. Inside that buffer is (the first PASS_MAX bytes of) the password, with the trailing newline yeeted, and it's terminated by a null byte ('\0').

⚠️ Heads up: that buffer may be overwritten by a following call. It's one buffer, shared, reused. So don't get attached, and definitely don't hold onto the pointer thinking it's yours 💀

On error? The terminal state gets restored, errno is set to indicate the error, and NULL is returned. Balance restored, but at what cost 😭

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💀 ERRORS 💀

• ENXIO — the process does not have a controlling terminal. no tty, no vibes, no password 🚫

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🍓 FILES 🍓

• /dev/tty

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🌈 ATTRIBUTES 🌈

For an explanation of the terms used in this section, see attributes(7).

• getpass() — Thread safety: MT-Unsafe term 🧵🚨

(it was a table in the original bestie, but tables are not the vibe here, so: one interface, one attribute, one value. that's the whole thing.)

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⭐ STANDARDS ⭐

None. 💀 literally none. she's not standardized, she's not claiming to be, she's just out here.

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🌸 HISTORY 🌸

• Version 7 AT&T UNIX 🦕
• Present in SUSv2, but marked LEGACY
• Removed in POSIX.1-2001 🪦

so yeah, she's been around, and she's been shown the door.

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🎀 NOTES 🎀

okay this is the part where we get real:

• You should use instead readpassphrase(3bsd), provided by libbsd. that's the upgrade, that's the main character, that's who you should be calling 💖
• In the GNU C library implementation, if /dev/tty cannot be opened, the prompt is written to stderr and the password is read from stdin. And ngl: there is no limit on the length of the password, and line editing is not disabled 🙈
• According to SUSv2, the value of PASS_MAX must be defined in <limits.h> in case it is smaller than 8, and can in any case be obtained using sysconf(_SC_PASS_MAX). However, POSIX.2 withdraws the constants PASS_MAX and _SC_PASS_MAX, and the function getpass(). The glibc version accepts _SC_PASS_MAX and returns BUFSIZ (e.g., 8192). yes, the lore is messy, we don't make the rules 😭

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😭 BUGS 😭

The calling process should zero the password as soon as possible to avoid leaving the cleartext password visible in the process's address space. Like, immediately bestie. Don't leave the cleartext just sitting there in memory, that's not the vibe, that's a whole security situation 🔥🚨

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🫶 SEE ALSO 🫶

• crypt(3)

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and that's the tea 💅 this lil rewrite was brought to you by Linux man-pages 6.20, dated 2026-07-02, from the getpass(3) page itself — stay safe, use readpassphrase(3bsd), and zero your buffers, ily 🎀✨🦋