Seeking Within a File
The last example showed a program that sequentially read through the /etc/motd file, copying it to standard output. Sometimes it is necessary to access portions of a file randomly. Perhaps your file represents a series of a million fixed-length records that must be retrieved at random. UNIX provides this functionality in the form of the lseek(2) function.
Applying lseek(2)
The lseek(2) function is actually a dual-purpose function. It not only allows the program to seek a specified offset within the open file, but the program can also find out what the current offset is, within the specified file. The function synopsis for lseek(2) is as follows:
#include <sys/types.h> #include <unistd.h> off_t lseek(int fildes, off_t offset, ...
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