Section 3.8. write Function

3.8. write Function

Data is written to an open file with the write function.

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 #include <unistd.h> ssize_t write(int filedes, const void *buf, size_t  nbytes);

Returns: number of bytes written if OK, 1 on error

The return value is usually equal to the nbytes argument; otherwise, an error has occurred. A common cause for a write error is either filling up a disk or exceeding the file size limit for a given process (Section 7.11 and Exercise 10.11).

For a regular file, the write starts at the file's current offset. If the O_APPEND option was specified when the file was opened, the file's offset is set to the current end of file before each write operation. After a successful write, the file's offset is incremented by the number of bytes actually written.