pipe / pipe2 - glibc

Split from the chapter glibc: stdio and Formatted I/O into the per-function layout; see the method page and the glibc ledger for coverage status.

Signature – int pipe(int pipefd[2]); int pipe2(int pipefd[2], int flags); – unistd.h.

Libc side – pipe returns 0 with pipefd[0] = read end and pipefd[1] = write end (the manual’s mnemonic: like stdin/stdout order), or -1+errno (EMFILE, ENFILE); on Linux the wrapper issues the pipe2 syscall (manual, Creating a Pipe). pipe2 is GNU (_GNU_SOURCE, symbol GLIBC_2.9) accepting O_CLOEXEC and O_NONBLOCK atomically – the fix for the FD_CLOEXEC race the flagless pipe cannot avoid. Writing to a pipe without readers raises SIGPIPE/EPIPE; writes up to PIPE_BUF are atomic (manual, Pipe Atomicity). mkfifo(path, mode) (sys/stat.h, POSIX.1) creates the named variant, a FIFO special file opened by name, returning 0/-1 (EEXIST, EROFS, ENOSPC, manual, FIFO Special Files).