ERRNO (3)

SYNOPSIS

#include <errno.h> extern int errno;

DESCRIPTION

The integer 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 errno .

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

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

Valid error numbers are all non-zero; errno 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, EDOM and ERANGE are in the ISO C standard. ISO C Amendment 1 defines the additional error number EILSEQ for coding errors in multibyte or wide characters.

E2BIG

Arg list too long

EACCES

Permission denied

EAGAIN

Resource temporarily unavailable

EBADF

Bad file descriptor

EBADMSG

Bad message

EBUSY

Resource busy

ECANCELED

Operation canceled

ECHILD

No child processes

EDEADLK

Resource deadlock avoided

EDOM

Domain error

EEXIST

File exists

EFAULT

Bad address

EFBIG

File too large

EINPROGRESS

Operation in progress

EINTR

Interrupted function call

EINVAL

Invalid argument

EIO

Input/output error

EISDIR

Is a directory

EMFILE

Too many open files

EMLINK

Too many links

EMSGSIZE

Inappropriate message buffer length

ENAMETOOLONG

Filename too long

ENFILE

Too many open files in system

ENODEV

No such device

ENOENT

No such file or directory

ENOEXEC

Exec format error

ENOLCK

No locks available

ENOMEM

Not enough space

ENOSPC

No space left on device

ENOSYS

Function not implemented

ENOTDIR

Not a directory

ENOTEMPTY

Directory not empty

ENOTSUP

Not supported

ENOTTY

Inappropriate I/O control operation

ENXIO

No such device or address

EPERM

Operation not permitted

EPIPE

Broken pipe

ERANGE

Result too large

EROFS

Read-only file system

ESPIPE

Invalid seek

ESRCH

No such process

ETIMEDOUT

Operation timed out

EXDEV

Improper link

Many other error numbers are returned by various Unix implementations. System V returns ETXTBSY (Text file busy) if one tries to exec() a file that is currently open for writing. Linux also returns this error if one tries to have a file both memory mapped with VM_DENYWRITE and open for writing.

SEE ALSO

- perror (3) - - strerror (3) - ' " ' " Copyright(c) 1989-1993 The Regents of the University of California ' " Copyright(c) 1994-1997 Sun Microsystems Inc ' " ' " See the file "license terms" for information on usage and redistribution ' " of this file and for a DISCLAIMER OF ALL WARRANTIES ' " ' " RCS: @(#) $Id: Eval (3) v 1 2 1998/09/14 18:39:48 stanton Exp $ ' " ' " The definitions below are for supplemental macros used in Tcl/Tk ' " manual entries ' " ' " AP type name in/out ?indent? ' " Start paragraph describing an argument to a library procedure ' " type is type of argument(int etc ) in/out is either "in" "out" ' " or "in/out" to describe whether procedure reads or modifies arg ' " and indent is equivalent to second arg of IP(shouldn't ever be ' " needed; use AS below instead) ' " ' " AS ?type? ?name? ' " Give maximum sizes of arguments for setting tab stops Type and ' " name are examples of largest possible arguments that will be passed ' " to AP later If args are omitted default tab stops are used ' " ' " BS ' " Start box enclosure From here until next BE everything will be ' " enclosed in one large box ' " ' " BE ' " End of box enclosure ' " ' " CS ' " Begin code excerpt ' " ' " CE ' " End code excerpt ' " ' " VS ?version? ?br? ' " Begin vertical sidebar for use in marking newly-changed parts ' " of man pages The first argument is ignored and used for recording ' " the version when the VS was added so that the sidebars can be ' " found and removed when they reach a certain age If another argument ' " is present then a line break is forced before starting the sidebar ' " ' " VE ' " End of vertical sidebar ' " ' " DS ' " Begin an indented unfilled display ' " ' " DE ' " End of indented unfilled display ' " ' " SO ' " Start of list of standard options for a Tk widget The ' " options follow on successive lines in four columns separated ' " by tabs ' " ' " SE ' " End of list of standard options for a Tk widget ' " ' " OP cmdName dbName dbClass ' " Start of description of a specific option cmdName gives the ' " option's name as specified in the class command dbName gives ' " the option's name in the option database and dbClass gives ' " the option's class in the option database ' " ' " UL arg1 arg2 ' " Print arg1 underlined then print arg2 normally ' " ' " RCS: @(#) $Id: man macros v 1 2 1998/09/14 18:39:54 stanton Exp $ ' " ' " # Set up traps and other miscellaneous stuff for Tcl/Tk man pages t wh -1 3i ^B ^l n( l b ' " # Start an argument description AP !" $4"" TP $4 { !" $2"" TP n()Cu 15