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Full Discussion: Function open() sets errno
Top Forums Programming Function open() sets errno Post 302826993 by DGPickett on Thursday 27th of June 2013 05:10:58 PM
Old 06-27-2013
Well open() returns an integer, which if -1 means errno is set to tell you what you did wrong. It sounds like your access in not good. You can set errno to zero before and test afterward. The nature of errno is that it is only set for errors, not reset on success. I usually:
Code:
if ( 0 > ( fd = open( file_name_ptr, O_RDONLY ))){
    perror( file_name_ptr );
    exit( 1 );
  }

This User Gave Thanks to DGPickett For This Post:
 

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mq_unlink(3)						     Library Functions Manual						      mq_unlink(3)

NAME
mq_unlink - Removes a message queue (P1003.1b) LIBRARY
Realtime Library (librt.so, librt.a) SYNOPSIS
#include <mqueue.h> int mq_unlink ( const char *name); PARAMETERS
*name Specifies a pointer to the pathname of a message queue. DESCRIPTION
The mq_unlink function removes a message queue named by the pathname. After a successful call to this function, subsequent calls to the mq_open function fail if they specify the queue identified by the name argument and the O_CREAT flag is not set. Close the connection to the queue with a call to the mq_close function before calling the mq_unlink function. If one or more processes have the message queue open when mq_unlink is called, destruction of the queue is postponed until all references to the message queue are removed. In this situation, the mq_unlink function returns immediately, without waiting for all queue references to be closed. RETURN VALUES
On successful completion, the function returns the value 0 (zero); otherwise, the function returns the value -1, sets errno to indicate the error, and the message queue remains. ERRORS
The mq_unlink function fails under the following conditions: [EACCES] Permission is denied to unlink the message queue. [ENAMETOOLONG] The length of the name string exceeds {NAME_MAX} while {_POSIX_NO_TRUNC} is in effect. [ENOENT] The named message queue does not exist. Additionally, any error that can be returned by the open or fstat file system calls can be returned by the mq_unlink function. RELATED INFORMATION
Functions: mq_close(3), mq_open(3) Guide to Realtime Programming delim off mq_unlink(3)
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