ERNO(3)                       Library functions                      ERNO(3)



NAME
       errno - number of last error

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  multi-
       byte or wide characters.


       E2BIG  Arg list too long

       EACES 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)



                                  1998-03-30                          ERNO(3)