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PROLOG |NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |EXAMPLES |APPLICATION USAGE |RATIONALE |FUTURE DIRECTIONS |SEE ALSO |COPYRIGHT | |
MKFIFO(3P) POSIX Programmer's ManualMKFIFO(3P)This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
mkfifo, mkfifoat — make a FIFO special file
#include <sys/stat.h> int mkfifo(const char *path, mode_tmode); #include <fcntl.h> int mkfifoat(intfd, const char *path, mode_tmode);
Themkfifo() function shall create a new FIFO special file named by the pathname pointed to bypath. The file permission bits of the new FIFO shall be initialized frommode. The file permission bits of themode argument shall be modified by the process' file creation mask. When bits inmode other than the file permission bits are set, the effect is implementation-defined. Ifpath names a symbolic link,mkfifo() shall fail and seterrno to[EEXIST]. The FIFO's user ID shall be set to the process' effective user ID. The FIFO's group ID shall be set to the group ID of the parent directory or to the effective group ID of the process. Implementations shall provide a way to initialize the FIFO's group ID to the group ID of the parent directory. Implementations may, but need not, provide an implementation-defined way to initialize the FIFO's group ID to the effective group ID of the calling process. Upon successful completion,mkfifo() shall mark for update the last data access, last data modification, and last file status change timestamps of the file. Also, the last data modification and last file status change timestamps of the directory that contains the new entry shall be marked for update. Themkfifoat() function shall be equivalent to themkfifo() function except in the case wherepath specifies a relative path. In this case the newly created FIFO is created relative to the directory associated with the file descriptorfd instead of the current working directory. If the access mode of the open file description associated with the file descriptor is not O_SEARCH, the function shall check whether directory searches are permitted using the current permissions of the directory underlying the file descriptor. If the access mode is O_SEARCH, the function shall not perform the check. Ifmkfifoat() is passed the special value AT_FDCWD in thefd parameter, the current working directory shall be used and the behavior shall be identical to a call tomkfifo().
Upon successful completion, these functions shall return 0. Otherwise, these functions shall return -1 and seterrno to indicate the error. If -1 is returned, no FIFO shall be created.
These functions shall fail if:EACCESA component of the path prefix denies search permission, or write permission is denied on the parent directory of the FIFO to be created.EEXISTThe named file already exists.ELOOPA loop exists in symbolic links encountered during resolution of thepath argument.ENAMETOOLONG The length of a component of a pathname is longer than {NAME_MAX}.ENOENTA component of the path prefix ofpath does not name an existing file orpath is an empty string.ENOENTorENOTDIR Thepath argument contains at least one non-<slash> character and ends with one or more trailing <slash> characters. Ifpath without the trailing <slash> characters would name an existing file, an[ENOENT]error shall not occur.ENOSPCThe directory that would contain the new file cannot be extended or the file system is out of file-allocation resources.ENOTDIR A component of the path prefix names an existing file that is neither a directory nor a symbolic link to a directory.EROFSThe named file resides on a read-only file system. Themkfifoat() function shall fail if:EACCESThe access mode of the open file description associated withfd is not O_SEARCH and the permissions of the directory underlyingfd do not permit directory searches.EBADFThepath argument does not specify an absolute path and thefd argument is neither AT_FDCWD nor a valid file descriptor open for reading or searching.ENOTDIR Thepath argument is not an absolute path andfd is a file descriptor associated with a non-directory file. These functions may fail if:ELOOPMore than {SYMLOOP_MAX} symbolic links were encountered during resolution of thepath argument.ENAMETOOLONG 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}.The following sections are informative.Creating a FIFO File The following example shows how to create a FIFO file named/home/cnd/mod_done, with read/write permissions for owner, and with read permissions for group and others. #include <sys/types.h> #include <sys/stat.h> int status; ... status = mkfifo("/home/cnd/mod_done", S_IWUSR | S_IRUSR | S_IRGRP | S_IROTH);None.
The syntax of this function is intended to maintain compatibility with historical implementations ofmknod(). The latter function was included in the 1984 /usr/group standard but only for use in creating FIFO special files. Themknod() function was originally excluded from the POSIX.1‐1988 standard as implementation-defined and replaced bymkdir() andmkfifo(). Themknod() function is now included for alignment with the Single UNIX Specification. The POSIX.1‐1990 standard required that the group ID of a newly created FIFO 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 usechown() to set the group ID after the FIFO is created, or determine under what conditions the implementation will set the desired group ID. The purpose of themkfifoat() function is to create a FIFO special file 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 tomkfifo(), resulting in unspecified behavior. By opening a file descriptor for the target directory and using themkfifoat() function it can be guaranteed that the newly created FIFO is located relative to the desired directory.
None.
chmod(3p),mknod(3p),umask(3p) The Base Definitions volume of POSIX.1‐2017,fcntl.h(0p),sys_stat.h(0p),sys_types.h(0p)
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. 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 athttp://www.opengroup.org/unix/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, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group 2017MKFIFO(3P)Pages that refer to this page:sys_stat.h(0p), mkfifo(1p), pax(1p), chmod(3p), mknod(3p), umask(3p)
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