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PROLOG |NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |EXAMPLES |APPLICATION USAGE |RATIONALE |FUTURE DIRECTIONS |SEE ALSO |COPYRIGHT | |
FSETPOS(3P) POSIX Programmer's ManualFSETPOS(3P)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.
fsetpos — set current file position
#include <stdio.h> int fsetpos(FILE *stream, const fpos_t *pos);
The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1‐2017 defers to the ISO C standard. Thefsetpos() function shall set the file position and state indicators for the stream pointed to bystream according to the value of the object pointed to bypos, which the application shall ensure is a value obtained from an earlier call tofgetpos() on the same stream. If a read or write error occurs, the error indicator for the stream shall be set andfsetpos() fails. A successful call to thefsetpos() function shall clear the end- of-file indicator for the stream and undo any effects ofungetc() on the same stream. After anfsetpos() call, the next operation on an update stream may be either input or output. The behavior offsetpos() on devices which are incapable of seeking is implementation-defined. The value of the file offset associated with such a device is undefined. Thefsetpos() function shall not change the setting oferrno if successful.
Thefsetpos() function shall return 0 if it succeeds; otherwise, it shall return a non-zero value and seterrno to indicate the error.
Thefsetpos() function shall fail if, either thestream is unbuffered or thestream's buffer needed to be flushed, and the call tofsetpos() causes an underlyinglseek() orwrite() to be invoked, and:EAGAINThe O_NONBLOCK flag is set for the file descriptor and the thread would be delayed in the write operation.EBADFThe file descriptor underlying the stream file is not open for writing or the stream's buffer needed to be flushed and the file is not open.EFBIGAn attempt was made to write a file that exceeds the maximum file size.EFBIGAn attempt was made to write a file that exceeds the file size limit of the process.EFBIGThe file is a regular file and an attempt was made to write at or beyond the offset maximum associated with the corresponding stream.EINTRThe write operation was terminated due to the receipt of a signal, and no data was transferred.EIOA physical I/O error has occurred, or the process is a member of a background process group attempting to perform awrite() to its controlling terminal, TOSTOP is set, the calling thread is not blocking SIGTTOU, the process is not ignoring SIGTTOU, and the process group of the process is orphaned. This error may also be returned under implementation-defined conditions.ENOSPCThere was no free space remaining on the device containing the file.EPIPEAn attempt was made to write to a pipe or FIFO that is not open for reading by any process; a SIGPIPE signal shall also be sent to the thread.ESPIPEThe file descriptor underlyingstream is associated with a pipe, FIFO, or socket. Thefsetpos() function may fail if:ENXIOA request was made of a nonexistent device, or the request was outside the capabilities of the device.The following sections are informative.
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Section 2.5,Standard I/O Streams,fopen(3p),ftell(3p),lseek(3p),rewind(3p),ungetc(3p),write(3p) The Base Definitions volume of POSIX.1‐2017,stdio.h(0p)
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 athttp://www.opengroup.org/unix/online.html . 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, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group 2017FSETPOS(3P)Pages that refer to this page:stdio.h(0p), fseek(3p), ungetc(3p), ungetwc(3p)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |