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Minix/2.0.0/wwwman/man2/open.2.html
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Minix/2.0.0/wwwman/man2/open.2.html
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<HTML>
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<TITLE>open(2)</TITLE>
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<BODY>
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<H1>open(2)</H1>
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<HR>
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<PRE>
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</PRE>
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<H2>NAME</H2><PRE>
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open - open a file for reading or writing, or create a new file
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</PRE>
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<H2>SYNOPSIS</H2><PRE>
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<STRONG>#include</STRONG> <STRONG><sys/types.h></STRONG>
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<STRONG>#include</STRONG> <STRONG><fcntl.h></STRONG>
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<STRONG>int</STRONG> <STRONG>open(const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>path</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>flags</EM> [<STRONG>,</STRONG> <STRONG>mode_t</STRONG> <EM>mode</EM>]<STRONG>)</STRONG>
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</PRE>
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<H2>DESCRIPTION</H2><PRE>
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<STRONG>Open</STRONG> opens the file <EM>path</EM> for reading and/or writing, as specified by the
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<EM>flags</EM> argument and returns a descriptor for that file. The <EM>flags</EM>
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argument may indicate the file is to be created if it does not already
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exist (by specifying the O_CREAT flag), in which case the file is created
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with mode <EM>mode</EM> as described in <STRONG><A HREF="../man2/chmod.2.html">chmod(2)</A></STRONG> and modified by the process'
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umask value (see <STRONG><A HREF="../man2/umask.2.html">umask(2)</A></STRONG>).
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<EM>Path</EM> is the address of a string of ASCII characters representing a path
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name, terminated by a null character. The flags specified are formed by
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<EM>or</EM>'ing the following values
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O_RDONLY open for reading only
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O_WRONLY open for writing only
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O_RDWR open for reading and writing
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O_NONBLOCK do not block on open
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O_APPEND append on each write
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O_CREAT create file if it does not exist
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O_TRUNC truncate size to 0
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O_EXCL error if create and file exists
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Opening a file with O_APPEND set causes each write on the file to be
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appended to the end. If O_TRUNC is specified and the file exists, the
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file is truncated to zero length. If O_EXCL is set with O_CREAT, then if
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the file already exists, the open returns an error. This can be used to
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implement a simple exclusive access locking mechanism. If O_EXCL is set
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and the last component of the pathname is a symbolic link, the open will
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fail even if the symbolic link points to a non-existent name. If the
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O_NONBLOCK flag is specified and the open call would result in the
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process being blocked for some reason, the open returns immediately.
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Upon successful completion a non-negative integer termed a file
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descriptor is returned. The file pointer used to mark the current
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position within the file is set to the beginning of the file.
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The new descriptor is set to remain open across <STRONG>execve</STRONG> system calls; see
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<STRONG><A HREF="../man2/close.2.html">close(2)</A></STRONG>.
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The system imposes a limit on the number of descriptors open
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simultaneously by one process.
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</PRE>
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<H2>ERRORS</H2><PRE>
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The named file is opened unless one or more of the following are true:
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[ENOTDIR] A component of the path prefix is not a directory.
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[ENAMETOOLONG] The path name exceeds PATH_MAX characters.
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[ENOENT] O_CREAT is not set and the named file does not exist.
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[ENOENT] A component of the path name that must exist does not
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exist.
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[EACCES] Search permission is denied for a component of the path
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prefix.
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[EACCES] The required permissions (for reading and/or writing) are
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denied for the named file.
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[EACCES] O_CREAT is specified, the file does not exist, and the
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directory in which it is to be created does not permit
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writing.
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[EACCES] A device to be opened for writing is physically write
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protected.
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[ELOOP] Too many symbolic links were encountered in translating
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the pathname. (Minix-vmd)
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[EISDIR] The named file is a directory, and the arguments specify
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it is to be opened for writing.
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[EROFS] The named file resides on a read-only file system, and the
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file is to be modified.
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[EMFILE] The system limit for open file descriptors per process has
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already been reached.
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[ENFILE] The system file table is full.
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[ENXIO] The named file is a character special or block special
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file, and the device associated with this special file
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does not exist.
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[ENOSPC] O_CREAT is specified, the file does not exist, and the
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directory in which the entry for the new file is being
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placed cannot be extended because there is no space left
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on the file system containing the directory.
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[ENOSPC] O_CREAT is specified, the file does not exist, and there
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are no free inodes on the file system on which the file is
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being created.
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[EIO] An I/O error occurred while making the directory entry or
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allocating the inode for O_CREAT.
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[EFAULT] <EM>Path</EM> points outside the process's allocated address space.
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[EEXIST] O_CREAT and O_EXCL were specified and the file exists.
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</PRE>
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<H2>SEE ALSO</H2><PRE>
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<STRONG><A HREF="../man2/chmod.2.html">chmod(2)</A></STRONG>, <STRONG><A HREF="../man2/close.2.html">close(2)</A></STRONG>, <STRONG><A HREF="../man2/dup.2.html">dup(2)</A></STRONG>, <STRONG><A HREF="../man2/fcntl.2.html">fcntl(2)</A></STRONG>, <STRONG><A HREF="../man2/lseek.2.html">lseek(2)</A></STRONG>, <STRONG><A HREF="../man2/read.2.html">read(2)</A></STRONG>, <STRONG><A HREF="../man2/write.2.html">write(2)</A></STRONG>,
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<STRONG><A HREF="../man2/umask.2.html">umask(2)</A></STRONG>.
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</PRE>
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</BODY>
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</HTML>
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