LSEEK(2) UNIX Programmer's Manual LSEEK(2) NAME lseek - move read/write pointer SYNOPSIS #include #define L_SET 0 /* set the seek pointer */ #define L_INCR 1 /* increment the seek pointer */ #define L_XTND 2 /* extend the file size */ pos = lseek(d, offset, whence) off_t pos; int d; off_t offset; int whence; DESCRIPTION The descriptor _d refers to a file or device open for reading and/or writing. _L_s_e_e_k sets the file pointer of _d as fol- lows: If _w_h_e_n_c_e is L_SET, the pointer is set to _o_f_f_s_e_t bytes. If _w_h_e_n_c_e is L_INCR, the pointer is set to its current location plus _o_f_f_s_e_t. If _w_h_e_n_c_e is L_XTND, the pointer is set to the size of the file plus _o_f_f_s_e_t. Upon successful completion, the resulting pointer location as measured in bytes from beginning of the file is returned. Some devices are incapable of seeking. The value of the pointer associated with such a device is undefined. NOTES Seeking far beyond the end of a file, then writing, creates a gap or "hole", which occupies no physical space and reads as zeros. RETURN VALUE Upon successful completion, the current file pointer value is returned. Otherwise, a value of -1 is returned and _e_r_r_n_o is set to indicate the error. ERRORS _L_s_e_e_k will fail and the file pointer will remain unchanged if: [EBADF] _F_i_l_d_e_s is not an open file descriptor. [ESPIPE] _F_i_l_d_e_s is associated with a pipe or a socket. Printed 11/26/99 February 24, 1986 1 LSEEK(2) UNIX Programmer's Manual LSEEK(2) [EINVAL] _W_h_e_n_c_e is not a proper value. SEE ALSO dup(2), open(2) BUGS This document's use of _w_h_e_n_c_e is incorrect English, but maintained for historical reasons. Printed 11/26/99 February 24, 1986 2