FTSNOCHDIR

FTSNOCHDIR refers to a flag used with the File Traversal System (FTS) library in Unix-like operating systems. When this flag is set, the traversal routines are instructed not to change the process’s current working directory (CWD) as they descend into the directory tree. This behavior can help avoid side effects from chdir calls and can improve predictability in programs that rely on stable paths or operate in multi-threaded contexts.

Usage and semantics

FTSNOCHDIR is used as a bitmask option passed to the fts_open function, typically together with other traversal flags such as FTS_PHYSICAL or FTS_LOGICAL. It is defined in the system header fts.h as part of the FTS interface. The practical effect is that the library will not perform chdir(2) during traversal, so the program must manage path handling itself. This makes the library more lightweight in terms of process state and can simplify certain path calculations.

Behavior and implications

With FTSNOCHDIR enabled, the caller should not assume that the current working directory changes as the traversal proceeds. Entry paths returned by the library (such as fts_path) may reflect absolute or seed-relative paths depending on the implementation and options used. Programs that rely on the CWD remaining constant should enable this flag to avoid unexpected directory changes.

Portability and history

FTS and its NOCHDIR flag originated with BSD Unix and were later incorporated into POSIX-compatible interfaces. Availability varies by platform and library implementation; most modern BSD variants and many Linux systems that provide the FTS interface support FTS_NOCHDIR, though exact semantics can differ slightly across environments.

See also

FTS, fts_open, fts_path, fts_read, fts_children, FTS_PHYSICAL, FTS_LOGICAL, FTS_NOCHDIR.