diff options
Diffstat (limited to 'man7/pipe.7')
-rw-r--r-- | man7/pipe.7 | 30 |
1 files changed, 15 insertions, 15 deletions
diff --git a/man7/pipe.7 b/man7/pipe.7 index baf05bc..bebb856 100644 --- a/man7/pipe.7 +++ b/man7/pipe.7 @@ -2,7 +2,7 @@ .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" -.TH pipe 7 2023-07-16 "Linux man-pages 6.05.01" +.TH pipe 7 2023-10-31 "Linux man-pages 6.7" .SH NAME pipe \- overview of pipes and FIFOs .SH DESCRIPTION @@ -14,7 +14,7 @@ and a .IR "write end" . Data written to the write end of a pipe can be read from the read end of the pipe. -.PP +.P A pipe is created using .BR pipe (2), which creates a new pipe and returns two file descriptors, @@ -24,7 +24,7 @@ Pipes can be used to create a communication channel between related processes; see .BR pipe (2) for an example. -.PP +.P A FIFO (short for First In First Out) has a name within the filesystem (created using .BR mkfifo (3)), @@ -48,7 +48,7 @@ The only difference between pipes and FIFOs is the manner in which they are created and opened. Once these tasks have been accomplished, I/O on pipes and FIFOs has exactly the same semantics. -.PP +.P If a process attempts to read from an empty pipe, then .BR read (2) will block until data is available. @@ -56,7 +56,7 @@ If a process attempts to write to a full pipe (see below), then .BR write (2) blocks until sufficient data has been read from the pipe to allow the write to complete. -.PP +.P Nonblocking I/O is possible by using the .BR fcntl (2) .B F_SETFL @@ -69,11 +69,11 @@ with If any process has the pipe open for writing, reads fail with .BR EAGAIN ; otherwise\[em]with no potential writers\[em]reads succeed and return empty. -.PP +.P The communication channel provided by a pipe is a .IR "byte stream" : there is no concept of message boundaries. -.PP +.P If all file descriptors referring to the write end of a pipe have been closed, then an attempt to .BR read (2) @@ -100,7 +100,7 @@ calls to close unnecessary duplicate file descriptors; this ensures that end-of-file and .BR SIGPIPE / EPIPE are delivered when appropriate. -.PP +.P It is not possible to apply .BR lseek (2) to a pipe. @@ -116,7 +116,7 @@ Applications should not rely on a particular capacity: an application should be designed so that a reading process consumes data as soon as it is available, so that a writing process does not remain blocked. -.PP +.P Before Linux 2.6.11, the capacity of a pipe was the same as the system page size (e.g., 4096 bytes on i386). Since Linux 2.6.11, the pipe capacity is 16 pages @@ -131,7 +131,7 @@ operations. See .BR fcntl (2) for more information. -.PP +.P The following .BR ioctl (2) operation, which can be applied to a file descriptor @@ -139,13 +139,13 @@ that refers to either end of a pipe, places a count of the number of unread bytes in the pipe in the .I int buffer pointed to by the final argument of the call: -.PP +.P .in +4n .EX ioctl(fd, FIONREAD, &nbytes); .EE .in -.PP +.P The .B FIONREAD operation is not specified in any standard, @@ -227,7 +227,7 @@ and attempts to increase a pipe's capacity will be denied. When the value of this limit is zero, no soft limit is applied. The default value for this file is 16384, which permits creating up to 1024 pipes with the default capacity. -.PP +.P Before Linux 4.9, some bugs affected the handling of the .I pipe\-user\-pages\-soft and @@ -310,7 +310,7 @@ a pipe or FIFO are .B O_NONBLOCK and .BR O_ASYNC . -.PP +.P Setting the .B O_ASYNC flag for the read end of a pipe causes a signal @@ -383,7 +383,7 @@ allocation could be pushed over the limit. Starting with Linux 4.9, the accounting step is performed before doing the allocation, and the operation fails if the limit would be exceeded. -.PP +.P Before Linux 4.9, bugs similar to points (a) and (c) could also occur when the kernel allocated memory for a new pipe buffer; that is, when calling |