Chdir

Chdir, short for change directory, is a function used in many operating system interfaces to modify the current working directory of the calling process. It is part of the POSIX standard and is exposed in C libraries as a system or library call; Windows provides a similar function such as _chdir in its C runtime. The primary purpose is to switch the process’s perspective of where relative paths begin.

The typical signature is int chdir(const char path). On success, it returns 0; on error, it returns -1 and sets errno to indicate the failure reason, such as ENOENT (no such file or directory), ENOTDIR (not a directory), or EACCES (permission denied). The path may be absolute or relative; when relative, it is interpreted with respect to the process’s current working directory. The process must have the necessary execute/search permissions for each component of the path.

The effect of chdir is confined to the process that invokes it. It changes the process’s own working directory, and this change is inherited by child processes created afterward. It does not alter the working directory of the calling process’s parent or sibling processes. In interactive shells, changing directories is typically implemented as a built-in command (for example, cd) so that the shell itself reflects the new directory.

High-level language wrappers commonly expose chdir-like functionality. For example, Python’s os.chdir() and other languages offer similar interfaces that internally call the underlying OS function. Handling errors and permissions is a common part of using chdir across languages and platforms.