.\" Copyright (c) 1996 Andries Brouwer (aeb@cwi.nl)
.\"
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.\" modify it under the terms of the GNU General Public License as
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.TH ERRNO 3 "30 March 1998" "" "Library functions"
.SH NAME
errno \- number of last error
.SH SYNOPSIS
#include <errno.h>
.sp
extern int errno;
.SH DESCRIPTION
The integer
.B errno
is set by system calls (and some library functions) to indicate
what went wrong.  Its value is significant only when the call
returned an error (usually \-1), and a library function that does succeed
is allowed to change
.BR errno .

Sometimes, when \-1 is also a legal return value one has to zero
.B errno
before the call in order to detect possible errors.

\fBerrno\fR is defined by the ISO C standard to be a modifiable lvalue
of type \fBint\fR, and must not be explicitly declared; \fBerrno\fR
may be a macro.  \fBerrno\fR is thread-local; setting it in one thread
does not affect its value in any other thread.

Valid error numbers are all non-zero; \fBerrno\fR is never set to zero
by any library function.  All the error names specified by POSIX.1
must have distinct values.

POSIX.1 (1996 edition) lists the following symbolic error names.  Of
these, \fBEDOM\fR and \fBERANGE\fR are in the ISO C standard.  ISO C
Amendment 1 defines the additional error number \fBEILSEQ\fR for
coding errors in multibyte or wide characters.

.TP
.B E2BIG
Arg list too long
.TP
.B EACCES
Permission denied
.TP
.B EAGAIN
Resource temporarily unavailable
.TP
.B EBADF
Bad file descriptor
.TP
.B EBADMSG
Bad message
.TP
.B EBUSY
Resource busy
.TP
.B ECANCELED
Operation canceled
.TP
.B ECHILD
No child processes
.TP
.B EDEADLK
Resource deadlock avoided
.TP
.B EDOM
Domain error
.TP
.B EEXIST
File exists
.TP
.B EFAULT
Bad address
.TP
.B EFBIG
File too large
.TP
.B EINPROGRESS
Operation in progress
.TP
.B EINTR
Interrupted function call
.TP
.B EINVAL
Invalid argument
.TP
.B EIO
Input/output error
.TP
.B EISDIR
Is a directory
.TP
.B EMFILE
Too many open files
.TP
.B EMLINK
Too many links
.TP
.B EMSGSIZE
Inappropriate message buffer length
.TP
.B ENAMETOOLONG
Filename too long
.TP
.B ENFILE
Too many open files in system
.TP
.B ENODEV
No such device
.TP
.B ENOENT
No such file or directory
.TP
.B ENOEXEC
Exec format error
.TP
.B ENOLCK
No locks available
.TP
.B ENOMEM
Not enough space
.TP
.B ENOSPC
No space left on device
.TP
.B ENOSYS
Function not implemented
.TP
.B ENOTDIR
Not a directory
.TP
.B ENOTEMPTY
Directory not empty
.TP
.B ENOTSUP
Not supported
.TP
.B ENOTTY
Inappropriate I/O control operation
.TP
.B ENXIO
No such device or address
.TP
.B EPERM
Operation not permitted
.TP
.B EPIPE
Broken pipe
.TP
.B ERANGE
Result too large
.TP
.B EROFS
Read-only file system
.TP
.B ESPIPE
Invalid seek
.TP
.B ESRCH
No such process
.TP
.B ETIMEDOUT
Operation timed out
.TP
.B EXDEV
Improper link


.SH "SEE ALSO"
.BR perror (3),
.BR strerror (3)