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flockfile(3)
NAME
  flockfile, ftrylockfilefunlockfile, stdio - locking functions

SYNOPSIS
  #include <stdio.h>

  void flockfile(
	  FILE * file );

  int ftrylockfile
	  FILE * file );

  void funlockfile
	  FILE * file );

LIBRARY
  Standard C Library (libc)

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  flockfile, funlockfile: POSIX.1c, XSH5.0

  ftrylockfile: XSH5.0

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  file
      Specifies the stream to be locked.

DESCRIPTION
  The flockfile(), ftrylockfile, and funlockfile functions provide for
  explicit application-level locking of stdio (FILE*) objects. These
  functions can be used by a thread to delineate a sequence of I/O statements
  that are to be executed as a unit.

  The flockfile() function locks a stdio stream so that a thread can have
  exclusive use of that stream for multiple I/O operations. Use the
  flockfile() function for a thread that wishes to ensure that the output of
  several printf() functions, for example, is not garbled by another thread
  also trying to use printf().

  The ftrylockfile() function is used by a thread to acquire ownership of a
  stdio (FILE*) object if the object is available. The ftrylockfile()
  function is a non-blocking version of flockfile().

  The funlockfile() function unlocks a stdio stream, causing the thread that
  had been holding the lock to relinquish exclusive use of the stream.

  The behavior of the flockfile() and funlockfile() functions is unspecified
  if the file parameter does not point to a valid FILE structure. The
  behavior of funlockfile() is also unspecified if a thread other than the
  current owner calls funlockfile().

  Matching flockfile() and funlockfile() calls can be nested. If the stream
  has been locked recursively, it will remain locked until the last matching
  funlockfile() is called.

RETURN VALUE
  None for flockfile() and funlockfile().  The ftrylockfile() function
  returns zero for success and non-zero to indicate that the lock cannot be
  acquired.

SEE ALSO
  Functions: getc_unlocked(3), putc_unlocked(3)

Index for Section 3

Alphabetical listing for F

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