Intro – introduction to system calls and error numbers
#include <errno.h>
This section describes all of the system calls. Most of these calls return one or more
error conditions. An error condition is indicated by an otherwise impossible return
value. This is almost always −1 or the null pointer; the individual descriptions specify
the details. An error number is also made available in the external variable errno,
which is not cleared on successful calls, so it should be tested only after an error has
been indicated.
In the case of multithreaded applications, the -mt option must be specified on the
command line at compilation time (see threads(3THR)). When the -mt option is
specified, errno becomes a macro that enables each thread to have its own errno.
This errno macro can be used on either side of the assignment as though it were a
variable.
Applications should use bound threads rather than the _lwp_*() functions (see
thr_create(3THR)). Using LWPs (lightweight processes) directly is not advised
because libraries are only safe to use with threads, not LWPs.
Each system call description attempts to list all possible error numbers. The following
is a complete list of the error numbers and their names as defined in <errno.h>.
1 EPERM Not superuser
Typically this error indicates an attempt to modify a file
in some way forbidden except to its owner or the
super-user. It is also returned for attempts by ordinary
users to do things allowed only to the super-user.
2 ENOENT No such file or directory
A file name is specified and the file should exist but
doesn’t, or one of the directories in a path name does
not exist.
3 ESRCH No such process, LWP, or thread
No process can be found in the system that
corresponds to the specified PID, LWPID_t,or
thread_t.
4 EINTR Interrupted system call
An asynchronous signal (such as interrupt or quit),
which the user has elected to catch, occurred during a
system service function. If execution is resumed after
processing the signal, it will appear as if the
interrupted function call returned this error condition.
Intro(2)
NAME
SYNOPSIS
DESCRIPTION
16 man pages section 2: System Calls • Last Revised 5 Nov 2001
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