When filename is the name of an existing file, acct() turns accounting on and appends a record to filename for each terminating process. When filename is NULL, acct() turns accounting off.
On success, 0 is returned.
On error, -1 is returned and
the global variable
errno is set appropriately.
BSD process accounting has not been enabled when the operating system kernel was compiled. The kernel configuration parameter controlling this feature is CONFIG_BSD_PROCESS_ACCT.
Out of memory.
The calling process has no permission to enable process accounting.
filename is not a regular file.
Error writing to the filename.
There are no more free file structures or we run out of memory.