term% cat index.txt WRITE(2) System Calls Manual WRITE(2)
NAME
write - write on a file
SYNOPSIS
write(fildes, buffer, nbytes)
char *buffer;
DESCRIPTION
Write writes data on the open file associated with the file descriptor.
Buffer is the address of nbytes contiguous bytes which are written on
the output file. The number of characters actually written is re‐
turned. It should be regarded as an error if this is not the same as
requested.
If the open file is being read by another process, data of at most one
write will be delivered to any read(2) in the other process. In par‐
ticular, if nbytes = 0, the read will return a count of 0, which is
conventionally taken to mean end of file.
Writes which are synchronized with file system blocks are more effi‐
cient than others; see filsys(5).
On some systems write clears the set-user-id bit on a file. This pre‐
vents penetration of system security by a user who captures a writable
set-user-id file that he does not own.
SEE ALSO
creat(2), open(2), pipe(2), select(2)
DIAGNOSTICS
Returns -1 on error: bad descriptor, buffer address, or count; physical
I/O errors.
WRITE(2)