OPEN

Section: MINTLIB LIBRARY FUNCTIONS (3)
Updated: 3 March 1993
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NAME

open - open or create a file for reading or writing

SYNOPSIS

#include <unistd.h>
#include <fcntl.h>

int open(const char *filename, int flags, ...);

DESCRIPTION

filename points to the pathname of a file. open opens the named file for reading and/or writing, as specified by the flags argument, and returns a descriptor for that file. The flags argument may indicate the file is to be created if it does not already exist (by specifying the O_CREAT flag). In this case an extra integer parameter pmode is used; the file is created with mode pmode as described in chmod and modified by the process' umask value (see umask). flags values are constructed by ORing flags from the following list (one and only one of the first three flags below must be used):

  - O_RDONLY  Open for reading only.
  - O_WRONLY  Open for writing only.
  - O_RDWR    Open for reading and writing.
  - O_NDELAY  Non-blocking I/O.
  - O_SYNC    Synchronize after writes (not implemented).
  - O_APPEND  If set, the seek pointer will be set to
              the end of the file prior to each write.
  - O_CREAT   Create the file if it doesn't exist already.
  - O_TRUNC   If the file exists and is a regular file,
              and the file is successfully opened using
              O_RDWR or O_WRONLY, its length is truncated
              to zero.
  - O_EXCL    If O_EXCL and O_CREAT are set, open will
              fail if the file exists. The seek pointer used to mark the current position within the file is set to the beginning of the file. The new descriptor is set to remain open across execve system calls; see close and fcntl.

RETURN VALUES

open returns a non-negative file descriptor on success. On failure, it returns -1 and sets errno to indicate the error.