01-24-2011
Quote:
Originally Posted by
Corona688
Just close it, if close succeeds it was open, if it wasn't, it was already closed...
yes,that's a good idea except i have to drop some status of the fd such as current position.Btw,thanks.
Quote:
Originally Posted by
Perderabo
Btw, fstat can tell you by succeeding or failing if fd n is open, but I see no reason for that here.
pls tell me some detail about that.I did't figure out some method to use "st_mode" to tell whether the fd is opened.Thanks a lot.
10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
I want to implement my own simple multi tasking shell in Unix which will take care of redirection (<, >, >>) and piping.
I am just unable to get a concrete idea of how exactly I have to start. I have several books...some are..
1. Maurice Bach- Design Of Unix Operating System
2. Richard... (3 Replies)
Discussion started by: clickonline1
3 Replies
2. Programming
I'm having difficulty understanding the purposes of using dup/dup2 when involving forks.
for example, if we call fork() once, that is, we are creating a child process. In what cases would we need to use dup or dup2 to duplicate the file descriptors for standard output and standard error? What... (1 Reply)
Discussion started by: Yifan_Guo
1 Replies
3. Programming
Hi,
i have in one program such a pice of code
................
static int old_stderr_handle = -1;
static int old_stdout_handle = -1;
log_handle = open(log_file_name,O_CREAT|O_RDWR,932);
old_stderr_handle = dup(STDERR_FILENO);
if (dup2(log_handle,STDERR_FILENO) < 0)
{
//... (1 Reply)
Discussion started by: vovan
1 Replies
4. UNIX for Advanced & Expert Users
int redirect()
{
int fd,rc;
fd = open("sample.DAT",O_CREAT | O_RDWR , 00777 );
rc = dup2(fd , 1 ) ;
close (fd );
return 0;
}
I used the above to redirect all the cout statements to sample.DAT. process is redirecting the output and I had two questions
1. All stdout/cout statements... (2 Replies)
Discussion started by: satish@123
2 Replies
5. UNIX for Advanced & Expert Users
Hey Guys
Some of my friends have got together and we are trying to write a basic kernel similar to Linux. I am trying to implement the malloc function in C and I am using a doubly linked list as the primary data structure. I need to allocate memory for this link list (duh...) and I don't feel... (2 Replies)
Discussion started by: rbansal2
2 Replies
6. Linux
Hi
I'm trying to implement CAPWAP protocol for my application.i'm able to configure my server side but i'm getting error at client(WTP) side as IOCTL error.while running the command
#./WTP /mnt/cf/capwap/
: wlan2
Starting WTP...
# WTP Loads... (0 Replies)
Discussion started by: ran789
0 Replies
7. UNIX for Dummies Questions & Answers
Hi everybody,
i've been googling for ages now and gotten kinda desperate... The question, however, might be rather trivial for the experts: What is it exactly, i.e. physically, the POSIX function (for a file) "lseek" does? Does it trigger some kind of synchronization on disk? Is it just for the... (4 Replies)
Discussion started by: Humudituu
4 Replies
8. UNIX for Advanced & Expert Users
is it possible to duplicate file descriptors(opened by a different process) with the help of dup or dup2. the two process do not share parent child relationship as well. (2 Replies)
Discussion started by: replytoshishir
2 Replies
9. Shell Programming and Scripting
I want to execute metasploit by two pipes to communicate with it, but I have troubles with that communication. When I run my program, I get this error: "stty: standard input: Inappropriate ioctl for device" and I don't receive the metasploit promt.
just select an exploit.
This is my code:... (2 Replies)
Discussion started by: dano88
2 Replies
10. Programming
What this code should do is: there are parent.cpp and child.cpp. Parent will send whatever is in the buffer to child and child will send back whatever received to parent. I do not know what I am doing wrong. I am confused what is missing in the parent and what else I should include into the child.... (1 Reply)
Discussion started by: ramono
1 Replies
LEARN ABOUT CENTOS
shell-quote
SHELL-QUOTE(1) User Contributed Perl Documentation SHELL-QUOTE(1)
NAME
shell-quote - quote arguments for safe use, unmodified in a shell command
SYNOPSIS
shell-quote [switch]... arg...
DESCRIPTION
shell-quote lets you pass arbitrary strings through the shell so that they won't be changed by the shell. This lets you process commands
or files with embedded white space or shell globbing characters safely. Here are a few examples.
EXAMPLES
ssh preserving args
When running a remote command with ssh, ssh doesn't preserve the separate arguments it receives. It just joins them with spaces and
passes them to "$SHELL -c". This doesn't work as intended:
ssh host touch 'hi there' # fails
It creates 2 files, hi and there. Instead, do this:
cmd=`shell-quote touch 'hi there'`
ssh host "$cmd"
This gives you just 1 file, hi there.
process find output
It's not ordinarily possible to process an arbitrary list of files output by find with a shell script. Anything you put in $IFS to
split up the output could legitimately be in a file's name. Here's how you can do it using shell-quote:
eval set -- `find -type f -print0 | xargs -0 shell-quote --`
debug shell scripts
shell-quote is better than echo for debugging shell scripts.
debug() {
[ -z "$debug" ] || shell-quote "debug:" "$@"
}
With echo you can't tell the difference between "debug 'foo bar'" and "debug foo bar", but with shell-quote you can.
save a command for later
shell-quote can be used to build up a shell command to run later. Say you want the user to be able to give you switches for a command
you're going to run. If you don't want the switches to be re-evaluated by the shell (which is usually a good idea, else there are
things the user can't pass through), you can do something like this:
user_switches=
while [ $# != 0 ]
do
case x$1 in
x--pass-through)
[ $# -gt 1 ] || die "need an argument for $1"
user_switches="$user_switches "`shell-quote -- "$2"`
shift;;
# process other switches
esac
shift
done
# later
eval "shell-quote some-command $user_switches my args"
OPTIONS
--debug
Turn debugging on.
--help
Show the usage message and die.
--version
Show the version number and exit.
AVAILABILITY
The code is licensed under the GNU GPL. Check http://www.argon.org/~roderick/ or CPAN for updated versions.
AUTHOR
Roderick Schertler <roderick@argon.org>
perl v5.16.3 2010-06-11 SHELL-QUOTE(1)