OPEN(3)                    POSIX Programmer's Manual                   OPEN(3)



PPRROOLLOOGG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.


NNAAMMEE
       open, openat -- open file relative to directory file descriptor

SSYYNNOOPPSSIISS
       #include <sys/stat.h>
       #include <fcntl.h>

       int open(const char *_p_a_t_h, int _o_f_l_a_g, ...);
       int openat(int _f_d, const char *_p_a_t_h, int _o_f_l_a_g, ...);

DDEESSCCRRIIPPTTIIOONN
       The _o_p_e_n() function shall establish the connection between a file and a
       file descriptor. It shall create an open file description that refers
       to a file and a file descriptor that refers to that open file
       description.  The file descriptor is used by other I/O functions to
       refer to that file. The _p_a_t_h argument points to a pathname naming the
       file.

       The _o_p_e_n() function shall return a file descriptor for the named file
       that is the lowest file descriptor not currently open for that process.
       The open file description is new, and therefore the file descriptor
       shall not share it with any other process in the system. The FD_CLOEXEC
       file descriptor flag associated with the new file descriptor shall be
       cleared unless the O_CLOEXEC flag is set in _o_f_l_a_g.

       The file offset used to mark the current position within the file shall
       be set to the beginning of the file.

       The file status flags and file access modes of the open file
       description shall be set according to the value of _o_f_l_a_g.

       Values for _o_f_l_a_g are constructed by a bitwise-inclusive OR of flags
       from the following list, defined in _<_f_c_n_t_l_._h_>.  Applications shall
       specify exactly one of the first five values (file access modes) below
       in the value of _o_f_l_a_g:

       O_EXEC        Open for execute only (non-directory files). The result
                     is unspecified if this flag is applied to a directory.

       O_RDONLY      Open for reading only.

       O_RDWR        Open for reading and writing. The result is undefined if
                     this flag is applied to a FIFO.

       O_SEARCH      Open directory for search only. The result is unspecified
                     if this flag is applied to a non-directory file.

       O_WRONLY      Open for writing only.

       Any combination of the following may be used:

       O_APPEND      If set, the file offset shall be set to the end of the
                     file prior to each write.

       O_CLOEXEC     If set, the FD_CLOEXEC flag for the new file descriptor
                     shall be set.

       O_CREAT       If the file exists, this flag has no effect except as
                     noted under O_EXCL below. Otherwise, the file shall be
                     created; the user ID of the file shall be set to the
                     effective user ID of the process; the group ID of the
                     file shall be set to the group ID of the file's parent
                     directory or to the effective group ID of the process;
                     and the access permission bits (see _<_s_y_s_/_s_t_a_t_._h_>) of the
                     file mode shall be set to the value of the argument
                     following the _o_f_l_a_g argument taken as type mmooddee__tt
                     modified as follows: a bitwise AND is performed on the
                     file-mode bits and the corresponding bits in the
                     complement of the process' file mode creation mask. Thus,
                     all bits in the file mode whose corresponding bit in the
                     file mode creation mask is set are cleared. When bits
                     other than the file permission bits are set, the effect
                     is unspecified. The argument following the _o_f_l_a_g argument
                     does not affect whether the file is open for reading,
                     writing, or for both. Implementations shall provide a way
                     to initialize the file's group ID to the group ID of the
                     parent directory. Implementations may, but need not,
                     provide an implementation-defined way to initialize the
                     file's group ID to the effective group ID of the calling
                     process.

       O_DIRECTORY   If _p_a_t_h resolves to a non-directory file, fail and set
                     _e_r_r_n_o to [[EENNOOTTDDIIRR]].

       O_DSYNC       Write I/O operations on the file descriptor shall
                     complete as defined by synchronized I/O data integrity
                     completion.

       O_EXCL        If O_CREAT and O_EXCL are set, _o_p_e_n() shall fail if the
                     file exists. The check for the existence of the file and
                     the creation of the file if it does not exist shall be
                     atomic with respect to other threads executing _o_p_e_n()
                     naming the same filename in the same directory with
                     O_EXCL and O_CREAT set. If O_EXCL and O_CREAT are set,
                     and _p_a_t_h names a symbolic link, _o_p_e_n() shall fail and set
                     _e_r_r_n_o to [[EEEEXXIISSTT]], regardless of the contents of the
                     symbolic link. If O_EXCL is set and O_CREAT is not set,
                     the result is undefined.

       O_NOCTTY      If set and _p_a_t_h identifies a terminal device, _o_p_e_n()
                     shall not cause the terminal device to become the
                     controlling terminal for the process. If _p_a_t_h does not
                     identify a terminal device, O_NOCTTY shall be ignored.

       O_NOFOLLOW    If _p_a_t_h names a symbolic link, fail and set _e_r_r_n_o to
                     [[EELLOOOOPP]].

       O_NONBLOCK    When opening a FIFO with O_RDONLY or O_WRONLY set:

                      *  If O_NONBLOCK is set, an _o_p_e_n() for reading-only
                         shall return without delay. An _o_p_e_n() for writing-
                         only shall return an error if no process currently
                         has the file open for reading.

                      *  If O_NONBLOCK is clear, an _o_p_e_n() for reading-only
                         shall block the calling thread until a thread opens
                         the file for writing. An _o_p_e_n() for writing-only
                         shall block the calling thread until a thread opens
                         the file for reading.

                     When opening a block special or character special file
                     that supports non-blocking opens:

                      *  If O_NONBLOCK is set, the _o_p_e_n() function shall
                         return without blocking for the device to be ready or
                         available. Subsequent behavior of the device is
                         device-specific.

                      *  If O_NONBLOCK is clear, the _o_p_e_n() function shall
                         block the calling thread until the device is ready or
                         available before returning.

                     Otherwise, the O_NONBLOCK flag shall not cause an error,
                     but it is unspecified whether the file status flags will
                     include the O_NONBLOCK flag.

       O_RSYNC       Read I/O operations on the file descriptor shall complete
                     at the same level of integrity as specified by the
                     O_DSYNC and O_SYNC flags. If both O_DSYNC and O_RSYNC are
                     set in _o_f_l_a_g, all I/O operations on the file descriptor
                     shall complete as defined by synchronized I/O data
                     integrity completion. If both O_SYNC and O_RSYNC are set
                     in flags, all I/O operations on the file descriptor shall
                     complete as defined by synchronized I/O file integrity
                     completion.

       O_SYNC        Write I/O operations on the file descriptor shall
                     complete as defined by synchronized I/O file integrity
                     completion.

                     The O_SYNC flag shall be supported for regular files,
                     even if the Synchronized Input and Output option is not
                     supported.

       O_TRUNC       If the file exists and is a regular file, and the file is
                     successfully opened O_RDWR or O_WRONLY, its length shall
                     be truncated to 0, and the mode and owner shall be
                     unchanged. It shall have no effect on FIFO special files
                     or terminal device files. Its effect on other file types
                     is implementation-defined. The result of using O_TRUNC
                     without either O_RDWR or O_WRONLY is undefined.

       O_TTY_INIT    If _p_a_t_h identifies a terminal device other than a pseudo-
                     terminal, the device is not already open in any process,
                     and either O_TTY_INIT is set in _o_f_l_a_g or O_TTY_INIT has
                     the value zero, _o_p_e_n() shall set any non-standard tteerrmmiiooss
                     structure terminal parameters to a state that provides
                     conforming behavior; see the Base Definitions volume of
                     POSIX.1-2008, _S_e_c_t_i_o_n _1_1_._2, _P_a_r_a_m_e_t_e_r_s _t_h_a_t _C_a_n _b_e _S_e_t.
                     It is unspecified whether O_TTY_INIT has any effect if
                     the device is already open in any process. If _p_a_t_h
                     identifies the slave side of a pseudo-terminal that is
                     not already open in any process, _o_p_e_n() shall set any
                     non-standard tteerrmmiiooss structure terminal parameters to a
                     state that provides conforming behavior, regardless of
                     whether O_TTY_INIT is set. If _p_a_t_h does not identify a
                     terminal device, O_TTY_INIT shall be ignored.

       If O_CREAT is set and the file did not previously exist, upon
       successful completion, _o_p_e_n() shall mark for update the last data
       access, last data modification, and last file status change timestamps
       of the file and the last data modification and last file status change
       timestamps of the parent directory.

       If O_TRUNC is set and the file did previously exist, upon successful
       completion, _o_p_e_n() shall mark for update the last data modification and
       last file status change timestamps of the file.

       If both the O_SYNC and O_DSYNC flags are set, the effect is as if only
       the O_SYNC flag was set.

       If _p_a_t_h refers to a STREAMS file, _o_f_l_a_g may be constructed from
       O_NONBLOCK OR'ed with either O_RDONLY, O_WRONLY, or O_RDWR. Other flag
       values are not applicable to STREAMS devices and shall have no effect
       on them. The value O_NONBLOCK affects the operation of STREAMS drivers
       and certain functions applied to file descriptors associated with
       STREAMS files. For STREAMS drivers, the implementation of O_NONBLOCK is
       device-specific.

       The application shall ensure that it specifies the O_TTY_INIT flag on
       the first open of a terminal device since system boot or since the
       device was closed by the process that last had it open. The application
       need not specify the O_TTY_INIT flag when opening pseudo-terminals.  If
       _p_a_t_h names the master side of a pseudo-terminal device, then it is
       unspecified whether _o_p_e_n() locks the slave side so that it cannot be
       opened. Conforming applications shall call _u_n_l_o_c_k_p_t() before opening
       the slave side.

       The largest value that can be represented correctly in an object of
       type ooffff__tt shall be established as the offset maximum in the open file
       description.

       The _o_p_e_n_a_t() function shall be equivalent to the _o_p_e_n() function except
       in the case where _p_a_t_h specifies a relative path. In this case the file
       to be opened is determined relative to the directory associated with
       the file descriptor _f_d instead of the current working directory. If the
       file descriptor was opened without O_SEARCH, the function shall check
       whether directory searches are permitted using the current permissions
       of the directory underlying the file descriptor. If the file descriptor
       was opened with O_SEARCH, the function shall not perform the check.

       The _o_f_l_a_g parameter and the optional fourth parameter correspond
       exactly to the parameters of _o_p_e_n().

       If _o_p_e_n_a_t() is passed the special value AT_FDCWD in the _f_d parameter,
       the current working directory shall be used and the behavior shall be
       identical to a call to _o_p_e_n().

RREETTUURRNN VVAALLUUEE
       Upon successful completion, these functions shall open the file and
       return a non-negative integer representing the lowest numbered unused
       file descriptor. Otherwise, these functions shall return -1 and set
       _e_r_r_n_o to indicate the error. If -1 is returned, no files shall be
       created or modified.

EERRRROORRSS
       These functions shall fail if:

       EEAACCCCEESS Search permission is denied on a component of the path prefix,
              or the file exists and the permissions specified by _o_f_l_a_g are
              denied, or the file does not exist and write permission is
              denied for the parent directory of the file to be created, or
              O_TRUNC is specified and write permission is denied.

       EEEEXXIISSTT O_CREAT and O_EXCL are set, and the named file exists.

       EEIINNTTRR  A signal was caught during _o_p_e_n().

       EEIINNVVAALL The implementation does not support synchronized I/O for this
              file.

       EEIIOO    The _p_a_t_h argument names a STREAMS file and a hangup or error
              occurred during the _o_p_e_n().

       EEIISSDDIIRR The named file is a directory and _o_f_l_a_g includes O_WRONLY or
              O_RDWR.

       EELLOOOOPP  A loop exists in symbolic links encountered during resolution of
              the _p_a_t_h argument, or O_NOFOLLOW was specified and the _p_a_t_h
              argument names a symbolic link.

       EEMMFFIILLEE All file descriptors available to the process are currently
              open.

       EENNAAMMEETTOOOOLLOONNGG
              The length of a component of a pathname is longer than
              {NAME_MAX}.

       EENNFFIILLEE The maximum allowable number of files is currently open in the
              system.

       EENNOOEENNTT O_CREAT is not set and a component of _p_a_t_h does not name an
              existing file, or O_CREAT is set and a component of the path
              prefix of _p_a_t_h does not name an existing file, or _p_a_t_h points to
              an empty string.

       EENNOOEENNTT or EENNOOTTDDIIRR
              O_CREAT is set, and the _p_a_t_h argument contains at least one
              non-<slash> character and ends with one or more trailing <slash>
              characters. If _p_a_t_h names an existing file, an [[EENNOOEENNTT]] error
              shall not occur.

       EENNOOSSRR  The _p_a_t_h argument names a STREAMS-based file and the system is
              unable to allocate a STREAM.

       EENNOOSSPPCC The directory or file system that would contain the new file
              cannot be expanded, the file does not exist, and O_CREAT is
              specified.

       EENNOOTTDDIIRR
              A component of the path prefix names an existing file that is
              neither a directory nor a symbolic link to a directory; or
              O_CREAT and O_EXCL are not specified, the _p_a_t_h argument contains
              at least one non-<slash> character and ends with one or more
              trailing <slash> characters, and the last pathname component
              names an existing file that is neither a directory nor a
              symbolic link to a directory; or O_DIRECTORY was specified and
              the _p_a_t_h argument resolves to a non-directory file.

       EENNXXIIOO  O_NONBLOCK is set, the named file is a FIFO, O_WRONLY is set,
              and no process has the file open for reading.

       EENNXXIIOO  The named file is a character special or block special file, and
              the device associated with this special file does not exist.

       EEOOVVEERRFFLLOOWW
              The named file is a regular file and the size of the file cannot
              be represented correctly in an object of type ooffff__tt.

       EERROOFFSS  The named file resides on a read-only file system and either
              O_WRONLY, O_RDWR, O_CREAT (if the file does not exist), or
              O_TRUNC is set in the _o_f_l_a_g argument.

       The _o_p_e_n_a_t() function shall fail if:

       EEAACCCCEESS _f_d was not opened with O_SEARCH and the permissions of the
              directory underlying _f_d do not permit directory searches.

       EEBBAADDFF  The _p_a_t_h argument does not specify an absolute path and the _f_d
              argument is neither AT_FDCWD nor a valid file descriptor open
              for reading or searching.

       EENNOOTTDDIIRR
              The _p_a_t_h argument is not an absolute path and _f_d is a file
              descriptor associated with a non-directory file.

       These functions may fail if:

       EEAAGGAAIINN The _p_a_t_h argument names the slave side of a pseudo-terminal
              device that is locked.

       EEIINNVVAALL The value of the _o_f_l_a_g argument is not valid.

       EELLOOOOPP  More than {SYMLOOP_MAX} symbolic links were encountered during
              resolution of the _p_a_t_h argument.

       EENNAAMMEETTOOOOLLOONNGG
              The length of a pathname exceeds {PATH_MAX}, or pathname
              resolution of a symbolic link produced an intermediate result
              with a length that exceeds {PATH_MAX}.

       EENNOOMMEEMM The _p_a_t_h argument names a STREAMS file and the system is unable
              to allocate resources.

       EETTXXTTBBSSYY
              The file is a pure procedure (shared text) file that is being
              executed and _o_f_l_a_g is O_WRONLY or O_RDWR.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
   OOppeenniinngg aa FFiillee ffoorr WWrriittiinngg bbyy tthhee OOwwnneerr
       The following example opens the file //ttmmpp//ffiillee, either by creating it
       (if it does not already exist), or by truncating its length to 0 (if it
       does exist). In the former case, if the call creates a new file, the
       access permission bits in the file mode of the file are set to permit
       reading and writing by the owner, and to permit reading only by group
       members and others.

       If the call to _o_p_e_n() is successful, the file is opened for writing.

           ##iinncclluuddee <<ffccnnttll..hh>>
           ......
           iinntt ffdd;;
           mmooddee__tt mmooddee == SS__IIRRUUSSRR || SS__IIWWUUSSRR || SS__IIRRGGRRPP || SS__IIRROOTTHH;;
           cchhaarr **ppaatthhnnaammee == ""//ttmmpp//ffiillee"";;
           ......
           ffdd == ooppeenn((ppaatthhnnaammee,, OO__WWRROONNLLYY || OO__CCRREEAATT || OO__TTRRUUNNCC,, mmooddee));;
           ......

   OOppeenniinngg aa FFiillee UUssiinngg aann EExxiisstteennccee CChheecckk
       The following example uses the _o_p_e_n() function to try to create the
       LLOOCCKKFFIILLEE file and open it for writing. Since the _o_p_e_n() function
       specifies the O_EXCL flag, the call fails if the file already exists.
       In that case, the program assumes that someone else is updating the
       password file and exits.

           ##iinncclluuddee <<ffccnnttll..hh>>
           ##iinncclluuddee <<ssttddiioo..hh>>
           ##iinncclluuddee <<ssttddlliibb..hh>>

           #define LOCKFILE "/etc/ptmp"
           ...
           int pfd; /* Integer for file descriptor returned by open() call. */
           ...
           if ((pfd = open(LOCKFILE, O_WRONLY | O_CREAT | O_EXCL,
               S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) == -1)
           {
               fprintf(stderr, "Cannot open /etc/ptmp. Try again later.\n");
               exit(1);
           }
           ...

   OOppeenniinngg aa FFiillee ffoorr WWrriittiinngg
       The following example opens a file for writing, creating the file if it
       does not already exist. If the file does exist, the system truncates
       the file to zero bytes.

           ##iinncclluuddee <<ffccnnttll..hh>>
           ##iinncclluuddee <<ssttddiioo..hh>>
           ##iinncclluuddee <<ssttddlliibb..hh>>

           #define LOCKFILE "/etc/ptmp"
           ...
           int pfd;
           char pathname[PATH_MAX+1];
           ...
           if ((pfd = open(pathname, O_WRONLY | O_CREAT | O_TRUNC,
               S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) == -1)
           {
               perror("Cannot open output file\n"); exit(1);
           }
           ...

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       POSIX.1-2008 does not require that terminal parameters be automatically
       set to any state on first open, nor that they be reset after the last
       close. It is possible for a non-conforming application to leave a
       terminal device in a state where the next process to use that device
       finds it in a non-conforming state, but has no way of determining this.
       To ensure that the device is set to a conforming initial state,
       applications which perform a first open of a terminal (other than a
       pseudo-terminal) should do so using the O_TTY_INIT flag to set the
       parameters associated with the terminal to a conforming state.

       Except as specified in this volume of POSIX.1-2008, the flags allowed
       in _o_f_l_a_g are not mutually-exclusive and any number of them may be used
       simultaneously. Not all combinations of flags make sense. For example,
       using O_SEARCH | O_CREAT will successfully open a pre-existing
       directory for searching, but if there is no existing file by that name,
       then it is unspecified whether a regular file will be created.
       Likewise, if a non-directory file descriptor is successfully returned,
       it is unspecified whether that descriptor will have execute permissions
       as if by O_EXEC (note that it is unspecified whether O_EXEC and
       O_SEARCH have the same value).

RRAATTIIOONNAALLEE
       Some implementations permit opening FIFOs with O_RDWR. Since FIFOs
       could be implemented in other ways, and since two file descriptors can
       be used to the same effect, this possibility is left as undefined.

       See _g_e_t_g_r_o_u_p_s() about the group of a newly created file.

       The use of _o_p_e_n() to create a regular file is preferable to the use of
       _c_r_e_a_t(), because the latter is redundant and included only for
       historical reasons.

       The use of the O_TRUNC flag on FIFOs and directories (pipes cannot be
       _o_p_e_n()-ed) must be permissible without unexpected side-effects (for
       example, _c_r_e_a_t() on a FIFO must not remove data). Since terminal
       special files might have type-ahead data stored in the buffer, O_TRUNC
       should not affect their content, particularly if a program that
       normally opens a regular file should open the current controlling
       terminal instead. Other file types, particularly implementation-defined
       ones, are left implementation-defined.

       POSIX.1-2008 permits [[EEAACCCCEESS]] to be returned for conditions other than
       those explicitly listed.

       The O_NOCTTY flag was added to allow applications to avoid
       unintentionally acquiring a controlling terminal as a side-effect of
       opening a terminal file. This volume of POSIX.1-2008 does not specify
       how a controlling terminal is acquired, but it allows an implementation
       to provide this on _o_p_e_n() if the O_NOCTTY flag is not set and other
       conditions specified in the Base Definitions volume of POSIX.1-2008,
       _C_h_a_p_t_e_r _1_1, _G_e_n_e_r_a_l _T_e_r_m_i_n_a_l _I_n_t_e_r_f_a_c_e are met.

       In historical implementations the value of O_RDONLY is zero. Because of
       that, it is not possible to detect the presence of O_RDONLY and another
       option. Future implementations should encode O_RDONLY and O_WRONLY as
       bit flags so that:

           OO__RRDDOONNLLYY || OO__WWRROONNLLYY ==== OO__RRDDWWRR

       O_EXEC and O_SEARCH are specified as two of the five file access modes.
       Since O_EXEC does not apply to directories, and O_SEARCH only applies
       to directories, their values need not be distinct. Since O_RDONLY has
       historically had the value zero, implementations are not able to
       distinguish between O_SEARCH and O_SEARCH | O_RDONLY, and similarly for
       O_EXEC.

       In general, the _o_p_e_n() function follows the symbolic link if _p_a_t_h names
       a symbolic link. However, the _o_p_e_n() function, when called with O_CREAT
       and O_EXCL, is required to fail with [[EEEEXXIISSTT]] if _p_a_t_h names an existing
       symbolic link, even if the symbolic link refers to a nonexistent file.
       This behavior is required so that privileged applications can create a
       new file in a known location without the possibility that a symbolic
       link might cause the file to be created in a different location.

       For example, a privileged application that must create a file with a
       predictable name in a user-writable directory, such as the user's home
       directory, could be compromised if the user creates a symbolic link
       with that name that refers to a nonexistent file in a system directory.
       If the user can influence the contents of a file, the user could
       compromise the system by creating a new system configuration or spool
       file that would then be interpreted by the system. The test for a
       symbolic link which refers to a nonexisting file must be atomic with
       the creation of a new file.

       In addition, the _o_p_e_n() function refuses to open non-directories if the
       O_DIRECTORY flag is set. This avoids race conditions whereby a user
       might compromise the system by substituting a hard link to a sensitive
       file (e.g., a device or a FIFO) while a privileged application is
       running, where opening a file even for read access might have
       undesirable side-effects.

       In addition, the _o_p_e_n() function does not follow symbolic links if the
       O_NOFOLLOW flag is set.  This avoids race conditions whereby a user
       might compromise the system by substituting a symbolic link to a
       sensitive file (e.g., a device) while a privileged application is
       running, where opening a file even for read access might have
       undesirable side-effects.

       The POSIX.1-1990 standard required that the group ID of a newly created
       file be set to the group ID of its parent directory or to the effective
       group ID of the creating process. FIPS 151-2 required that
       implementations provide a way to have the group ID be set to the group
       ID of the containing directory, but did not prohibit implementations
       also supporting a way to set the group ID to the effective group ID of
       the creating process.  Conforming applications should not assume which
       group ID will be used. If it matters, an application can use _c_h_o_w_n() to
       set the group ID after the file is created, or determine under what
       conditions the implementation will set the desired group ID.

       The purpose of the _o_p_e_n_a_t() function is to enable opening files in
       directories other than the current working directory without exposure
       to race conditions. Any part of the path of a file could be changed in
       parallel to a call to _o_p_e_n(), resulting in unspecified behavior. By
       opening a file descriptor for the target directory and using the
       _o_p_e_n_a_t() function it can be guaranteed that the opened file is located
       relative to the desired directory. Some implementations use the
       _o_p_e_n_a_t() function for other purposes as well. In some cases, if the
       _o_f_l_a_g parameter has the O_XATTR bit set, the returned file descriptor
       provides access to extended attributes. This functionality is not
       standardized here.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _c_h_m_o_d(), _c_l_o_s_e(), _c_r_e_a_t(), _d_i_r_f_d(), _d_u_p(), _e_x_e_c, _f_c_n_t_l(), _f_d_o_p_e_n_d_i_r(),
       _l_i_n_k(), _l_s_e_e_k(), _m_k_d_t_e_m_p(), _m_k_n_o_d(), _r_e_a_d(), _s_y_m_l_i_n_k(), _u_m_a_s_k(),
       _u_n_l_o_c_k_p_t(), _w_r_i_t_e()

       The Base Definitions volume of POSIX.1-2008, _C_h_a_p_t_e_r _1_1, _G_e_n_e_r_a_l
       _T_e_r_m_i_n_a_l _I_n_t_e_r_f_a_c_e, <<ffccnnttll..hh>>, <<ssyyss__ssttaatt..hh>>, <<ssyyss__ttyyppeess..hh>>

CCOOPPYYRRIIGGHHTT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be obtained online
       at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2013                              OPEN(3)
