PR_Open

Opens a file for reading, writing, or both. Also used to create a file.

Syntax

#include <prio.h>

PRFileDesc* PR_Open(
  const char *name,
  PRIntn flags,
  PRIntn mode);

Parameters

The function has the following parameters:

name: The pathname of the file to be opened.
flags: The file status flags define how the file is accessed. It is a bitwise OR of the following bit flags. In most cases, only one of the first three flags may be used. If the flags parameter does not include any of the first three flags (PR_RDONLY, PR_WRONLY, or PR_RDWR), the open file can’t be read or written, which is not useful.

Note

The constants PR_RDWR and friends are not in any interface (bug 433295). Thus they cannot be used in JavaScript, you have to use the octal constants (see File I/O Snippets).

Name	Value	Description
`PR_RDONLY`	0x01	Open for reading only.
`PR_WRONLY`	0x02	Open for writing only.
`PR_RDWR`	0x04	Open for reading and writing.
`PR_CREATE_FILE`	0x08	If the file does not exist, the file is created. If the file exists, this flag has no effect.
`PR_APPEND`	0x10	The file pointer is set to the end of the file prior to each write.
`PR_TRUNCATE`	0x20	If the file exists, its length is truncated to 0.
`PR_SYNC`	0x40	If set, each write will wait for both the file data and file status to be physically updated.
`PR_EXCL`	0x80	With `PR_CREATE_FILE`, if the file does not exist, the file is created. If the file already exists, no action and NULL is returned.

mode: When PR_CREATE_FILE flag is set and the file is created, these flags define the access permission bits of the newly created file. This feature is currently only applicable on Unix platforms. It is ignored by any other platform but it may apply to other platforms in the future. Possible values of the mode parameter are listed in the table below.

Name	Value	Description
`PR_IRWXU`	0700	read, write, execute/search by owner.
`PR_IRUSR`	0400	read permission, owner.
`PR_IWUSR`	0200	write permission, owner.
`PR_IXUSR`	0100	execute/search permission, owner.
`PR_IRWXG`	0070	read, write, execute/search by group
`PR_IRGRP`	0040	read permission, group
`PR_IWGRP`	0020	write permission, group
`PR_IXGRP`	0010	execute/search permission, group
`PR_IRWXO`	0007	read, write, execute/search by others
`PR_IROTH`	0004	read permission, others
`PR_IWOTH`	0002	write permission, others
`PR_IXOTH`	0001	execute/search permission, others

Returns

The function returns one of the following values:

If the file is successfully opened, a pointer to a dynamically allocated PRFileDesc for the newly opened file. The PRFileDesc should be freed by calling PR_Close.
If the file was not opened successfully, a NULL pointer.

Description

PR_Open creates a file descriptor (PRFileDesc) for the file with the pathname name and sets the file status flags of the file descriptor according to the value of flags. If a new file is created as a result of the PR_Open call, its file mode bits are set according to the mode parameter.