The <errno.h> header file defines the integer variable errno, which is
set by system calls and some library functions in the event of an error
to indicate what went wrong. Its value is significant only when the
return value of the call indicated an error (i.e., -1 from most system
calls; -1 or NULL from most library functions); a function that suc-
ceeds is allowed to change errno.
So, errno should never be used to check whether an error happened -- only which error. It's easy to picture more elaborate library calls changing the value of errno many times before they return... You must be exact about when and why you use it for what to get something meaningful.
I'm not sure why a successful system call would be changing errno, but it's allowed to. Perhaps it was a simplification -- "these first 4 cases will all return EACCESS, so set it first, and return immediately if any of them fail". And they never bother to change the error to success when it succeeds.
Another invalid way to use errno is checking the value of errno too late, after they've made another system call. This can give you the strange result 'ERROR: Success'.
Last edited by Corona688; 06-27-2013 at 06:48 PM..
I need to write a function that will work in sh/ksh shell that will test to see if a file has already been opened for writting by another user
has anyone written something like this? (3 Replies)
timbass
Sat, 28 Jul 2007 10:07:53 +0000
Originally posted in Yahoo! CEP-Interest
Here is my follow-up note on posets (partially ordered sets) and tosets (totally or linearly ordered sets) as background set theory for event processing, and in particular CEP and ESP.
In my last note, we... (0 Replies)
We are a tool vendor and one of our users is getting this error.
The user is using several macrovision(FLEXLM) license enabled products including ours.
(lmgrd) Can't open /usr/tmp/.flexlm/lmgrdl.4081, errno: 24
At this time, it stops checking out licenses, and will not
respond to query's.... (2 Replies)
Hey, Can I assume that for certain function calls, errno can never be set to a certain value.
More specifically, can I assume that for if the stat function call fails, the errno can never be or "No space left on device."
I am assuming that a read function cannot fail because of no space... (5 Replies)
To begin:
I use Linux
The Problem:
I need bcp functionality for scripts. Perl modules, such as Sybase:xfer, require ctlib which comes with Sybase Open Client. Talking with Sybase sales
reps is an exercise in futility and hate. They know absolutely nothing about their own products and will... (0 Replies)
If a process already has the entire file locked for read and write using newstruct.l_type = F_WRLCK; what would happen if another process would try to open it in read only mode using open(filename, O_RDONLY); ?
I want to check if the file exists and I want it to work even if another process has... (4 Replies)
Help Please perl Gurus,
I am trying to add ungrouped passengers in a group and I creating a script however it fails on first step only I tried all the options it returns following error.
syntax error at junki line 4, near "open "
Execution of junki aborted due to compilation errors. ... (2 Replies)
Hello all, just a quick little part of code i'm writing to check if the file i'm writing too in my automatic process is not being written too manually.
#!/bin/bash
FUSER=$(/sbin/fuser -s /toto.tmp >/dev/null 2>&1)
LSOF=$(/usr/sbin/lsof | grep -q "toto.tmp")
PGREP=$(pgrep -f "toto.tmp" >... (6 Replies)
Hi,
Unable to make tape backup, please help.
/opt/ignite/bin/make_tape_recovery -a /dev/rmt/?mn -I -v -m tar -x inc_entire=vg00
* Creating local directories for configuration files and archive.
======= 04/25/16 16:28:08 IST Started /opt/ignite/bin/make_tape_recovery.
(Mon... (4 Replies)
Discussion started by: anuragr
4 Replies
LEARN ABOUT DEBIAN
flopen
FLOPEN(3) BSD Library Functions Manual FLOPEN(3)NAME
flopen -- reliably open and lock a file
LIBRARY
Utility functions from BSD systems (libbsd, -lbsd)
SYNOPSIS
#include <sys/fcntl.h>
#include <bsd/libutil.h>
int
flopen(const char *path, int flags);
int
flopen(const char *path, int flags, mode_t mode);
DESCRIPTION
The flopen() function opens or creates a file and acquires an exclusive lock on it. It is essentially equivalent with calling open() with
the same parameters followed by flock() with an operation argument of LOCK_EX, except that flopen() will attempt to detect and handle races
that may occur between opening / creating the file and locking it. Thus, it is well suited for opening lock files, PID files, spool files,
mailboxes and other kinds of files which are used for synchronization between processes.
If flags includes O_NONBLOCK and the file is already locked, flopen() will fail and set errno to EWOULDBLOCK.
As with open(), the additional mode argument is required if flags includes O_CREAT.
RETURN VALUES
If successful, flopen() returns a valid file descriptor. Otherwise, it returns -1, and sets errno as described in flock(2) and open(2).
SEE ALSO errno(2), flock(2), open(2)AUTHORS
The flopen function and this manual page were written by Dag-Erling Smorgrav <des@FreeBSD.org>.
BSD June 6, 2009 BSD