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32 .\" @(#)fseek.3 8.1 (Berkeley) 6/4/93
46 .Nd reposition a stream
52 .Fn fseek "FILE *stream" "long offset" "int whence"
54 .Fn ftell "FILE *stream"
56 .Fn rewind "FILE *stream"
58 .Fn fgetpos "FILE * restrict stream" "fpos_t * restrict pos"
60 .Fn fsetpos "FILE *stream" "const fpos_t *pos"
63 .Fn fseeko "FILE *stream" "off_t offset" "int whence"
65 .Fn ftello "FILE *stream"
69 function sets the file position indicator for the stream pointed
72 The new position, measured in bytes, is obtained by adding
74 bytes to the position specified by
83 the offset is relative to the
84 start of the file, the current position indicator, or end-of-file,
86 A successful call to the
88 function clears the end-of-file indicator for the stream and undoes
93 functions on the same stream.
98 obtains the current value of the file position indicator for the
104 function sets the file position indicator for the stream pointed
107 to the beginning of the file.
110 .Dl (void)fseek(stream, 0L, SEEK_SET)
112 except that the error indicator for the stream is also cleared
118 does not return a value,
119 an application wishing to detect errors should clear
125 is non-zero, assume an error has occurred.
129 function is identical to
138 function is identical to
148 are alternate interfaces for retrieving and setting the current position in
153 except that the current position is stored in an opaque object of
158 These functions provide a portable way to seek to offsets larger than
159 those that can be represented by a
161 They may also store additional state information in the
163 object to facilitate seeking within files containing multibyte
164 characters with state-dependent encodings.
167 has traditionally been an integral type,
168 applications cannot assume that it is;
169 in particular, they must not perform arithmetic on objects
172 If the stream is a wide character stream (see
174 the position specified by the combination of
178 must contain the first byte of a multibyte sequence.
185 .Rv -std fgetpos fseek fseeko fsetpos
187 Upon successful completion,
191 return the current offset.
192 Otherwise, \-1 is returned and the global variable
194 is set to indicate the error.
201 is not a seekable stream.
205 argument is invalid or
206 the resulting file-position
207 indicator would be set to a negative value.
209 The resulting file offset would be a value which
210 cannot be represented correctly in an object of type
223 The file descriptor underlying stream is associated with a pipe or FIFO
224 or file-position indicator value is unspecified
238 may also fail and set
240 for any of the errors specified for the routines