F_GETPIPE_SZ(2const) - Linux manual page (original) (raw)

FGETPIPESZ(2const) FGETPIPESZ(2const)

NAME top

   F_GETPIPE_SZ, F_SETPIPE_SZ - get/set the capacity of a pipe

LIBRARY top

   Standard C library (_libc_, _-lc_)

SYNOPSIS top

   **#define _GNU_SOURCE**
   **#include <fcntl.h>**

   **int fcntl(int** _fd_**, F_SETPIPE_SZ, int** _arg_**);**
   **int fcntl(int** _fd_**, F_GETPIPE_SZ);**

DESCRIPTION top

   **F_SETPIPE_SZ**
          Change the capacity of the pipe referred to by _fd_ to be at
          least _arg_ bytes.  An unprivileged process can adjust the
          pipe capacity to any value between the system page size and
          the limit defined in _/proc/sys/fs/pipe-max-size_ (see
          [proc_sys_fs(5)](../man5/proc%5Fsys%5Ffs.5.html)).  Attempts to set the pipe capacity below
          the page size are silently rounded up to the page size.
          Attempts by an unprivileged process to set the pipe
          capacity above the limit in _/proc/sys/fs/pipe-max-size_
          yield the error **EPERM**; a privileged process
          (**CAP_SYS_RESOURCE**) can override the limit.

          When allocating the buffer for the pipe, the kernel may use
          a capacity larger than _arg_, if that is convenient for the
          implementation.  (In the current implementation, the
          allocation is the next higher power-of-two page-size
          multiple of the requested size.)  The actual capacity (in
          bytes) that is set is returned as the function result.

          Attempting to set the pipe capacity smaller than the amount
          of buffer space currently used to store data produces the
          error **EBUSY**.

          Note that because of the way the pages of the pipe buffer
          are employed when data is written to the pipe, the number
          of bytes that can be written may be less than the nominal
          size, depending on the size of the writes.

   **F_GETPIPE_SZ**
          Return (as the function result) the capacity of the pipe
          referred to by _fd_.

RETURN VALUE top

   The pipe capacity.

   On error, -1 is returned, and _[errno](../man3/errno.3.html)_ is set to indicate the error.

ERRORS top

   See [fcntl(2)](../man2/fcntl.2.html).

   **EBUSY** _op_ is **F_SETPIPE_SZ** and the new pipe capacity specified in
          _arg_ is smaller than the amount of buffer space currently
          used to store data in the pipe.

   **EPERM** _op_ is **F_SETPIPE_SZ** and the soft or hard user pipe limit has
          been reached; see [pipe(7)](../man7/pipe.7.html).

STANDARDS top

   Linux.

HISTORY top

   Linux 2.6.35.

SEE ALSO top

   [fcntl(2)](../man2/fcntl.2.html)

COLOPHON top

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Linux man-pages 6.15 2025-07-20 FGETPIPESZ(2const)

Pages that refer to this page:fcntl(2)