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26 .\" changed section from 2 to 3, aeb, 950919
28 .TH MKFIFO 3 2021-03-22 "GNU" "Linux Programmer's Manual"
30 mkfifo, mkfifoat \- make a FIFO special file (a named pipe)
33 .B #include <sys/types.h>
34 .B #include <sys/stat.h>
36 .BI "int mkfifo(const char *" pathname ", mode_t " mode );
38 .BR "#include <fcntl.h> " "/* Definition of AT_* constants */"
39 .B #include <sys/stat.h>
41 .BI "int mkfifoat(int " dirfd ", const char *" pathname ", mode_t " mode );
45 Feature Test Macro Requirements for glibc (see
46 .BR feature_test_macros (7)):
52 _POSIX_C_SOURCE >= 200809L
58 makes a FIFO special file with name \fIpathname\fP.
59 \fImode\fP specifies the FIFO's permissions.
61 process's \fBumask\fP in the usual way: the permissions of the created
62 file are \fB(\fP\fImode\fP\fB & \(tiumask)\fP.
64 A FIFO special file is similar to a pipe, except that it is created
66 Instead of being an anonymous communications
67 channel, a FIFO special file is entered into the filesystem by
71 Once you have created a FIFO special file in this way, any process can
72 open it for reading or writing, in the same way as an ordinary file.
73 However, it has to be open at both ends simultaneously before you can
74 proceed to do any input or output operations on it.
75 Opening a FIFO for reading normally blocks until some
76 other process opens the same FIFO for writing, and vice versa.
79 for nonblocking handling of FIFO special files.
83 function operates in exactly the same way as
85 except for the differences described here.
87 If the pathname given in
89 is relative, then it is interpreted relative to the directory
90 referred to by the file descriptor
92 (rather than relative to the current working directory of
93 the calling process, as is done by
95 for a relative pathname).
105 is interpreted relative to the current working
106 directory of the calling process (like
117 for an explanation of the need for
125 On error, \-1 is returned and
127 is set to indicate the error.
131 One of the directories in \fIpathname\fP did not allow search
132 (execute) permission.
135 The user's quota of disk blocks or inodes on the filesystem has been
139 \fIpathname\fP already exists.
140 This includes the case where
142 is a symbolic link, dangling or not.
145 Either the total length of \fIpathname\fP is greater than
146 \fBPATH_MAX\fP, or an individual filename component has a length
147 greater than \fBNAME_MAX\fP.
148 In the GNU system, there is no imposed
149 limit on overall filename length, but some filesystems may place
150 limits on the length of a component.
153 A directory component in \fIpathname\fP does not exist or is a
154 dangling symbolic link.
157 The directory or filesystem has no room for the new file.
160 A component used as a directory in \fIpathname\fP is not, in fact, a
164 \fIpathname\fP refers to a read-only filesystem.
166 The following additional errors can occur for
175 nor a valid file descriptor.
179 is a relative pathname and
181 is a file descriptor referring to a file other than a directory.
184 was added to glibc in version 2.4.
185 It is implemented using
187 available on Linux since kernel 2.6.16.
189 For an explanation of the terms used in this section, see
197 Interface Attribute Value
201 T} Thread safety MT-Safe
208 POSIX.1-2001, POSIX.1-2008.