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diff --git a/man-pages-posix-2017/man3p/pipe.3p b/man-pages-posix-2017/man3p/pipe.3p new file mode 100644 index 0000000..a56a498 --- /dev/null +++ b/man-pages-posix-2017/man3p/pipe.3p @@ -0,0 +1,174 @@ +'\" et +.TH PIPE "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual" +.\" +.SH PROLOG +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. +.\" +.SH NAME +pipe +\(em create an interprocess channel +.SH SYNOPSIS +.LP +.nf +#include <unistd.h> +.P +int pipe(int \fIfildes\fP[2]); +.fi +.SH DESCRIPTION +The +\fIpipe\fR() +function shall create a pipe and place two file descriptors, one +each into the arguments +.IR fildes [0] +and +.IR fildes [1], +that refer to the open file descriptions for the read and write ends of +the pipe. The file descriptors shall be allocated as described in +.IR "Section 2.14" ", " "File Descriptor Allocation". +The O_NONBLOCK and FD_CLOEXEC flags shall be clear on both file +descriptors. (The +\fIfcntl\fR() +function can be used to set both these flags.) +.P +Data can be written to the file descriptor +.IR fildes [1] +and read from the file descriptor +.IR fildes [0]. +A read on the file descriptor +.IR fildes [0] +shall access data written to the file descriptor +.IR fildes [1] +on a first-in-first-out basis. It is unspecified whether +.IR fildes [0] +is also open for writing and whether +.IR fildes [1] +is also open for reading. +.P +A process has the pipe open for reading (correspondingly writing) if it +has a file descriptor open that refers to the read end, +.IR fildes [0] +(write end, +.IR fildes [1]). +.P +The pipe's user ID shall be set to the effective user ID of the +calling process. +.P +The pipe's group ID shall be set to the effective group ID of the +calling process. +.P +Upon successful completion, +\fIpipe\fR() +shall mark for update the last data access, last data modification, +and last file status change timestamps of the pipe. +.SH "RETURN VALUE" +Upon successful completion, 0 shall be returned; otherwise, \-1 shall +be returned and +.IR errno +set to indicate the error, no file descriptors shall be allocated and +the contents of +.IR fildes +shall be left unmodified. +.SH ERRORS +The +\fIpipe\fR() +function shall fail if: +.TP +.BR EMFILE +All, or all but one, of the file descriptors available to the process +are currently open. +.TP +.BR ENFILE +The number of simultaneously open files in the system would exceed a +system-imposed limit. +.LP +.IR "The following sections are informative." +.SH EXAMPLES +.SS "Using a Pipe to Pass Data Between a Parent Process and a Child Process" +.P +The following example demonstrates the use of a pipe to transfer data +between a parent process and a child process. Error handling is +excluded, but otherwise this code demonstrates good practice when using +pipes: after the +\fIfork\fR() +the two processes close the unused ends of the pipe before they +commence transferring data. +.sp +.RS 4 +.nf + +#include <stdlib.h> +#include <unistd.h> +\&... +.P +int fildes[2]; +const int BSIZE = 100; +char buf[BSIZE]; +ssize_t nbytes; +int status; +.P +status = pipe(fildes); +if (status == -1 ) { + /* an error occurred */ + ... +} +.P +switch (fork()) { +case -1: /* Handle error */ + break; +.P +case 0: /* Child - reads from pipe */ + close(fildes[1]); /* Write end is unused */ + nbytes = read(fildes[0], buf, BSIZE); /* Get data from pipe */ + /* At this point, a further read would see end-of-file ... */ + close(fildes[0]); /* Finished with pipe */ + exit(EXIT_SUCCESS); +.P +default: /* Parent - writes to pipe */ + close(fildes[0]); /* Read end is unused */ + write(fildes[1], "Hello world\en", 12); /* Write data on pipe */ + close(fildes[1]); /* Child will see EOF */ + exit(EXIT_SUCCESS); +} +.fi +.P +.RE +.SH "APPLICATION USAGE" +None. +.SH RATIONALE +The wording carefully avoids using the verb ``to open'' in order to +avoid any implication of use of +\fIopen\fR(); +see also +\fIwrite\fR(). +.SH "FUTURE DIRECTIONS" +None. +.SH "SEE ALSO" +.IR "Section 2.14" ", " "File Descriptor Allocation", +.IR "\fIfcntl\fR\^(\|)", +.IR "\fIread\fR\^(\|)", +.IR "\fIwrite\fR\^(\|)" +.P +The Base Definitions volume of POSIX.1\(hy2017, +.IR "\fB<fcntl.h>\fP", +.IR "\fB<unistd.h>\fP" +.\" +.SH COPYRIGHT +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 at +http://www.opengroup.org/unix/online.html . +.PP +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 . |