PMSTRNCPY(3)

💖 PMSTRNCPY(3) — safe string copy 💖

okay bestie, this one's from the Library Functions Manual and it's genuinely one of the good ones, so grab a boba and let's go 🧋✨

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🌸 NAME 🌸

pmstrncpy — safe string copy 🫶

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✨ C SYNOPSIS ✨

#include <pcp/pmapi.h>

int pmstrncpy(char *dest, size_t destlen, char *src);

cc ... -lpcp

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🦋 DESCRIPTION 🦋

pmstrncpy is the safe string copying routine, with semantics kinda similar to strncpy(3). note the kinda — she's giving "inspired by, but evolved" 💅

The main differences between pmstrncpy and strncpy(3) are, and I need you to pay attention because this is the whole point:

• src must be null-byte terminated for pmstrncpy 🌟
• pmstrncpy makes sure that dest is null-byte terminated, even when src is larger than destlen; this may result in truncated copying of src ✂️
• when src is shorter than destlen, pmstrncpy does not null-byte fill the remainder of dest after src has been copied and null-byte terminated 🕳️
• the length argument has the same semantics for pmstrncpy and pmstrncat(3), unlike strncpy(3) and strncat(3) — consistency queen 👑
• the return value from pmstrncpy is actually useful 😭 (revolutionary, I know)
• the order of the arguments for pmstrncpy has been deliberately changed from the order of the arguments for strncpy(3), to avoid accidental misuse that a compiler can easily detect 🚨

On success, pmstrncpy returns 0, else -1 indicates that src is too big and the result has been truncated to ensure dest has not been overrun 🔥

not me being obsessed with a function that tells you when it cut something off. communication!! we love to see it 🎀

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💀 HISTORY 💀

strncpy(3) first appeared in Edition 7 AT&T Unix around 1979. she was specifically crafted to copy file names from component names from on-disk directory entries that were of a fixed maximum size, and may have zero, one or more trailing null-bytes. very niche. very specific. very much not a general-purpose string copier 🙈

The subsequent attempts to use strncpy(3) for more general string copying operations has been fraught with abuse and security issues; pmstrncpy is an attempt to address these problems. so basically: the group chat learned from the drama, and now we have boundaries ✨

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👑 SEE ALSO 👑

PMAPI(3), pmstrncat(3), strncat(3) and strncpy(3) — go read the whole friend group, they're all connected 🫶

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that's the whole page bestie, no cap 💖 this one's brought to you by Performance Co-Pilot / PCP, and yeah, she's literally still titled PMSTRNCPY(3) at the bottom too. periodt 💅🌈