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LSEEK(2) BSD System Calls Manual LSEEK(2) NAME lseek -- reposition read/write file offset LIBRARY Standard C Library (libc, -lc) SYNOPSIS #include <unistd.h> off_t lseek(int fildes, off_t offset, int whence); DESCRIPTION The lseek() system call repositions the offset of the file descriptor fildes to the argument offset according to the directive whence. The ar- gument fildes must be an open file descriptor. The lseek() system call repositions the file position pointer associated with the file descriptor fildes as follows: If whence is SEEK_SET, the offset is set to offset bytes. If whence is SEEK_CUR, the offset is set to its current location plus offset bytes. If whence is SEEK_END, the offset is set to the size of the file plus offset bytes. The lseek() system call allows the file offset to be set beyond the end of the existing end-of-file of the file. If data is later written at this point, subsequent reads of the data in the gap return bytes of zeros (until data is actually written into the gap). Some devices are incapable of seeking. The value of the pointer associ- ated with such a device is undefined. RETURN VALUES Upon successful completion, lseek() returns the resulting offset location as measured in bytes from the beginning of the file. Otherwise, a value of -1 is returned and errno is set to indicate the error. ERRORS The lseek() system call will fail and the file position pointer will re- main unchanged if: [EBADF] The fildes argument is not an open file descriptor. [EINVAL] The whence argument is not a proper value or the re- sulting file offset would be negative for a non-char- acter special file. [EOVERFLOW] The resulting file offset would be a value which can- not be represented correctly in an object of type off_t. [ESPIPE] The fildes argument is associated with a pipe, socket, or FIFO. SEE ALSO dup(2), open(2) BUGS This document's use of whence is incorrect English, but is maintained for historical reasons. STANDARDS The lseek() system call is expected to conform to ISO/IEC 9945-1:1990 ("POSIX.1"). HISTORY The lseek() function appeared in Version 7 AT&T UNIX. BSD April 19, 1994 BSD
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | BUGS | STANDARDS | HISTORY
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