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Diffstat (limited to 'man3/fread.3')
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diff --git a/man3/fread.3 b/man3/fread.3 new file mode 100644 index 0000000..2874d43 --- /dev/null +++ b/man3/fread.3 @@ -0,0 +1,165 @@ +'\" t +.\" Copyright (c) 1990, 1991 The Regents of the University of California. +.\" and Copyright (c) 2020 Arkadiusz Drabczyk <arkadiusz@drabczyk.org> +.\" All rights reserved. +.\" +.\" This code is derived from software contributed to Berkeley by +.\" Chris Torek and the American National Standards Committee X3, +.\" on Information Processing Systems. +.\" +.\" SPDX-License-Identifier: BSD-4-Clause-UC +.\" +.\" @(#)fread.3 6.6 (Berkeley) 6/29/91 +.\" +.\" Converted for Linux, Mon Nov 29 15:37:33 1993, faith@cs.unc.edu +.\" Sun Feb 19 21:26:54 1995 by faith, return values +.\" Modified Thu Apr 20 20:43:53 1995 by Jim Van Zandt <jrv@vanzandt.mv.com> +.\" Modified Fri May 17 10:21:51 1996 by Martin Schulze <joey@infodrom.north.de> +.\" +.TH fread 3 2023-07-20 "Linux man-pages 6.05.01" +.SH NAME +fread, fwrite \- binary stream input/output +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <stdio.h> +.PP +.BI "size_t fread(void " ptr "[restrict ." size " * ." nmemb ], +.BI " size_t " size ", size_t " nmemb , +.BI " FILE *restrict " stream ); +.BI "size_t fwrite(const void " ptr "[restrict ." size " * ." nmemb ], +.BI " size_t " size ", size_t " nmemb , +.BI " FILE *restrict " stream ); +.fi +.SH DESCRIPTION +The function +.BR fread () +reads +.I nmemb +items of data, each +.I size +bytes long, from the stream pointed to by +.IR stream , +storing them at the location given by +.IR ptr . +.PP +The function +.BR fwrite () +writes +.I nmemb +items of data, each +.I size +bytes long, to the stream pointed to by +.IR stream , +obtaining them from the location given by +.IR ptr . +.PP +For nonlocking counterparts, see +.BR unlocked_stdio (3). +.SH RETURN VALUE +On success, +.BR fread () +and +.BR fwrite () +return the number of items read or written. +This number equals the number of bytes transferred only when +.I size +is 1. +If an error occurs, or the end of the file is reached, +the return value is a short item count (or zero). +.PP +The file position indicator for the stream is advanced by the number +of bytes successfully read or written. +.PP +.BR fread () +does not distinguish between end-of-file and error, and callers must use +.BR feof (3) +and +.BR ferror (3) +to determine which occurred. +.SH ATTRIBUTES +For an explanation of the terms used in this section, see +.BR attributes (7). +.TS +allbox; +lbx lb lb +l l l. +Interface Attribute Value +T{ +.na +.nh +.BR fread (), +.BR fwrite () +T} Thread safety MT-Safe +.TE +.sp 1 +.SH STANDARDS +C11, POSIX.1-2008. +.SH HISTORY +POSIX.1-2001, C89. +.SH EXAMPLES +The program below demonstrates the use of +.BR fread () +by parsing /bin/sh ELF executable in binary mode and printing its +magic and class: +.PP +.in +4n +.EX +$ \fB./a.out\fP +ELF magic: 0x7f454c46 +Class: 0x02 +.EE +.in +.SS Program source +\& +.\" SRC BEGIN (fread.c) +.EX +#include <stdio.h> +#include <stdlib.h> +\& +#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0])) +\& +int +main(void) +{ + FILE *fp; + size_t ret; + unsigned char buffer[4]; +\& + fp = fopen("/bin/sh", "rb"); + if (!fp) { + perror("fopen"); + return EXIT_FAILURE; + } +\& + ret = fread(buffer, sizeof(*buffer), ARRAY_SIZE(buffer), fp); + if (ret != ARRAY_SIZE(buffer)) { + fprintf(stderr, "fread() failed: %zu\en", ret); + exit(EXIT_FAILURE); + } +\& + printf("ELF magic: %#04x%02x%02x%02x\en", buffer[0], buffer[1], + buffer[2], buffer[3]); +\& + ret = fread(buffer, 1, 1, fp); + if (ret != 1) { + fprintf(stderr, "fread() failed: %zu\en", ret); + exit(EXIT_FAILURE); + } +\& + printf("Class: %#04x\en", buffer[0]); +\& + fclose(fp); +\& + exit(EXIT_SUCCESS); +} +.EE +.\" SRC END +.SH SEE ALSO +.BR read (2), +.BR write (2), +.BR feof (3), +.BR ferror (3), +.BR unlocked_stdio (3) |