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| .TH MKFIFO 3 2021-03-22 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| mkfifo, mkfifoat \- make a FIFO special file (a named pipe) |
| .SH SYNOPSIS |
| .nf |
| .B #include <sys/types.h> |
| .B #include <sys/stat.h> |
| .PP |
| .BI "int mkfifo(const char *" pathname ", mode_t " mode ); |
| .PP |
| .BR "#include <fcntl.h> " "/* Definition of AT_* constants */" |
| .B #include <sys/stat.h> |
| .PP |
| .BI "int mkfifoat(int " dirfd ", const char *" pathname ", mode_t " mode ); |
| .fi |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR mkfifoat (): |
| .nf |
| Since glibc 2.10: |
| _POSIX_C_SOURCE >= 200809L |
| Before glibc 2.10: |
| _ATFILE_SOURCE |
| .fi |
| .SH DESCRIPTION |
| .BR mkfifo () |
| makes a FIFO special file with name \fIpathname\fP. |
| \fImode\fP specifies the FIFO's permissions. |
| It is modified by the |
| process's \fBumask\fP in the usual way: the permissions of the created |
| file are \fB(\fP\fImode\fP\fB & \(tiumask)\fP. |
| .PP |
| A FIFO special file is similar to a pipe, except that it is created |
| in a different way. |
| Instead of being an anonymous communications |
| channel, a FIFO special file is entered into the filesystem by |
| calling |
| .BR mkfifo (). |
| .PP |
| Once you have created a FIFO special file in this way, any process can |
| open it for reading or writing, in the same way as an ordinary file. |
| However, it has to be open at both ends simultaneously before you can |
| proceed to do any input or output operations on it. |
| Opening a FIFO for reading normally blocks until some |
| other process opens the same FIFO for writing, and vice versa. |
| See |
| .BR fifo (7) |
| for nonblocking handling of FIFO special files. |
| .SS mkfifoat() |
| The |
| .BR mkfifoat () |
| function operates in exactly the same way as |
| .BR mkfifo (), |
| except for the differences described here. |
| .PP |
| If the pathname given in |
| .I pathname |
| is relative, then it is interpreted relative to the directory |
| referred to by the file descriptor |
| .I dirfd |
| (rather than relative to the current working directory of |
| the calling process, as is done by |
| .BR mkfifo () |
| for a relative pathname). |
| .PP |
| If |
| .I pathname |
| is relative and |
| .I dirfd |
| is the special value |
| .BR AT_FDCWD , |
| then |
| .I pathname |
| is interpreted relative to the current working |
| directory of the calling process (like |
| .BR mkfifo ()). |
| .PP |
| If |
| .I pathname |
| is absolute, then |
| .I dirfd |
| is ignored. |
| .SH RETURN VALUE |
| On success |
| .BR mkfifo () |
| and |
| .BR mkfifoat () |
| return 0. |
| On error, \-1 is returned and |
| .I errno |
| is set to indicate the error. |
| .SH ERRORS |
| .TP |
| .B EACCES |
| One of the directories in \fIpathname\fP did not allow search |
| (execute) permission. |
| .TP |
| .B EDQUOT |
| The user's quota of disk blocks or inodes on the filesystem has been |
| exhausted. |
| .TP |
| .B EEXIST |
| \fIpathname\fP already exists. |
| This includes the case where |
| .I pathname |
| is a symbolic link, dangling or not. |
| .TP |
| .B ENAMETOOLONG |
| Either the total length of \fIpathname\fP is greater than |
| \fBPATH_MAX\fP, or an individual filename component has a length |
| greater than \fBNAME_MAX\fP. |
| In the GNU system, there is no imposed |
| limit on overall filename length, but some filesystems may place |
| limits on the length of a component. |
| .TP |
| .B ENOENT |
| A directory component in \fIpathname\fP does not exist or is a |
| dangling symbolic link. |
| .TP |
| .B ENOSPC |
| The directory or filesystem has no room for the new file. |
| .TP |
| .B ENOTDIR |
| A component used as a directory in \fIpathname\fP is not, in fact, a |
| directory. |
| .TP |
| .B EROFS |
| \fIpathname\fP refers to a read-only filesystem. |
| .PP |
| The following additional errors can occur for |
| .BR mkfifoat (): |
| .TP |
| .B EBADF |
| .I dirfd |
| is not a valid file descriptor. |
| .TP |
| .B ENOTDIR |
| .I pathname |
| is a relative path and |
| .I dirfd |
| is a file descriptor referring to a file other than a directory. |
| .SH VERSIONS |
| .BR mkfifoat () |
| was added to glibc in version 2.4. |
| It is implemented using |
| .BR mknodat (2), |
| available on Linux since kernel 2.6.16. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR mkfifo (), |
| .BR mkfifoat () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| .BR mkfifo (): |
| POSIX.1-2001, POSIX.1-2008. |
| .PP |
| .BR mkfifoat (): |
| POSIX.1-2008. |
| .SH SEE ALSO |
| .BR mkfifo (1), |
| .BR close (2), |
| .BR open (2), |
| .BR read (2), |
| .BR stat (2), |
| .BR umask (2), |
| .BR write (2), |
| .BR fifo (7) |