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NAMEwrite - write to a file descriptor
DESCRIPTIONwrite writes up to count bytes to the file referenced by the file descriptor fd from the buffer starting at buf. POSIX requires that a fBread()fP which can be proved to occur after a fBwrite()fP has returned returns the new data. Note that not all file systems are POSIX conforming.
RETURN VALUEOn success, the number of bytes written are returned (zero indicates nothing was written). On error, -1 is returned, and fIerrnofP is set appropriately. If fIcountfP is zero and the file descriptor refers to a regular file, 0 will be returned without causing any other effect. For a special file, the results are not portable.
CONFORMING TOSVr4, SVID, POSIX, X/OPEN, 4.3BSD. SVr4 documents additional error conditions EDEADLK, ENOLCK, ENOLNK, ENOSR, ENXIO, or ERANGE. Under SVr4 a write may be interrupted and return EINTR at any point, not just before any data is written.
NOTESA successful return from write does not make any guarantee that data has been committed to disk. In fact, on some buggy implementations, it does not even guarantee that space has successfully been reserved for the data. The only way to be sure is to call fsync(2) after you are done writing all your data.
SEE ALSOclose(2), fcntl(2), fsync(2), ioctl(2), lseek(2), open(2), read(2), select(2), fwrite(3), writev(3)