getcwd (nr 79)

Linux Signature

char *getcwd(char *buf, size_t size);

Description

Copies the absolute pathname of the current working directory into buf. On success, returns buf. On failure, returns -1 and sets errno.

Current Implementation

1. Validates that buf is within user address space. Returns -EFAULT (-14) if not.
2. Reads the cwd field from the current process’s Process struct.
3. Checks that size is large enough to hold the cwd string plus a null terminator. Returns -ERANGE (-34) if too small.
4. Copies the cwd string and null terminator into the user buffer.
5. Returns buf (the pointer value) on success — matching Linux’s behaviour where the return value is the buffer address.

Each process has its own cwd field (default "/"), updated by chdir.

Source: osl/src/syscalls/fs.rs — sys_getcwd

Usage from C (musl)

#include <unistd.h>

char buf[256];
if (getcwd(buf, sizeof(buf)) != NULL) {
    /* buf contains the current working directory */
}

Or via raw syscall:

#include <sys/syscall.h>

char buf[256];
long ret = syscall(SYS_getcwd, buf, sizeof(buf));
/* ret > 0 on success (pointer to buf) */

Future Work

• Support getcwd(NULL, 0) which auto-allocates a buffer (musl handles this in userspace).