xref: /freebsd/lib/libc/stdio/fread.3 (revision a220d00e74dd245b4fca59c5eca0c53963686325)
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36.\"     @(#)fread.3	8.2 (Berkeley) 3/8/94
37.\" $FreeBSD$
38.\"
39.Dd March 8, 1994
40.Dt FREAD 3
41.Os
42.Sh NAME
43.Nm fread ,
44.Nm fwrite
45.Nd binary stream input/output
46.Sh LIBRARY
47.Lb libc
48.Sh SYNOPSIS
49.In stdio.h
50.Ft size_t
51.Fn fread "void *ptr" "size_t size" "size_t nmemb" "FILE *stream"
52.Ft size_t
53.Fn fwrite "const void *ptr" "size_t size" "size_t nmemb" "FILE *stream"
54.Sh DESCRIPTION
55The function
56.Fn fread
57reads
58.Fa nmemb
59objects, each
60.Fa size
61bytes long, from the stream pointed to by
62.Fa stream ,
63storing them at the location given by
64.Fa ptr .
65.Pp
66The function
67.Fn fwrite
68writes
69.Fa nmemb
70objects, each
71.Fa size
72bytes long, to the stream pointed to by
73.Fa stream ,
74obtaining them from the location given by
75.Fa ptr .
76.Sh RETURN VALUES
77The functions
78.Fn fread
79and
80.Fn fwrite
81advance the file position indicator for the stream
82by the number of bytes read or written.
83They return the number of objects read or written.
84If an error occurs, or the end-of-file is reached,
85the return value is a short object count (or zero).
86.Pp
87The function
88.Fn fread
89does not distinguish between end-of-file and error, and callers
90must use
91.Xr feof 3
92and
93.Xr ferror 3
94to determine which occurred.
95The function
96.Fn fwrite
97returns a value less than
98.Fa nmemb
99only if a write error has occurred.
100.Sh SEE ALSO
101.Xr read 2 ,
102.Xr write 2
103.Sh STANDARDS
104The functions
105.Fn fread
106and
107.Fn fwrite
108conform to
109.St -isoC .
110