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Old 06-05-2003, 01:49 PM   #1
Linh
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C program code to run a Linux command line


I would like a C program code to run a Linux command line such as ifconfig, testparm and others.

Below is a simple C program code, what command would I use so that this little program will execute the command ifconfig. If there is any syntax error below, please fix it also.

========================================
#include <stdio.h>

int main()

{
char *linux-command []
linux-command = "ifconfig"

# What function would I call so that linux-command would be
# execute as if the user in on a command line console.

}
 
Old 06-05-2003, 01:51 PM   #2
acid_kewpie
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Please do not post the same thread in more than one forum. Picking the most relevant forum and posting it once there makes it easier for other members to help you and keeps the discussion all in one place.

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Old 06-05-2003, 02:02 PM   #3
kev82
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system, defined in stdlib.h. check out man 3 system for definition
 
Old 06-05-2003, 04:19 PM   #4
kev82
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please post on the forum and dont email me personally, thank you

i am not a linux programmer so this probably isnt perfect. do you know what pipes are? if not read about them. there is a function in stdio, popen that returns a FILE pointer but for a pipe instead of a file. read about popen then try the following

FILE *f;
f = popen("ls", "r");

// here you can use f as you would any normal FILE pointer but it
// contains the output of the ls command

pclose(f);

obviously you want to add some error checking in there and replace ls with ifconfig or whatever command you want to execute.
 
Old 06-07-2003, 03:10 AM   #5
Gopal
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// You can use system() function

#include <stdio.h>
int main()
{
system("clear");
system("ifconfig");

}
 
Old 06-09-2003, 12:20 PM   #6
tcaptain
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I'm assuming that this would also apply to C++?

(I've been searching for info on this, but didn't know what to ask myself).
 
Old 06-10-2003, 05:33 PM   #7
coolman0stress
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Yes, you can use stdio.h in C++ as well. Basically with a few rare incompatibilites, you can use anything in C in C++.
 
Old 06-10-2003, 08:39 PM   #8
tcaptain
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Quote:
Originally posted by Gopal
// You can use system() function

#include <stdio.h>
int main()
{
system("clear");
system("ifconfig");

}
When you use the system function like that? Where does the output go? (The man page doesn't mention...)
 
Old 06-10-2003, 11:02 PM   #9
coolman0stress
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Well, my assumption is the output is displayed to the screen, like is the case with system("ls");

Now the more interesting question is, is there anyway to *capture* the output and use it directly in your program?

Obviously you could send the ouput of the command to a file and then read from the file. No, i am talking about whether or not you can do it without creating any files.

*Goes of hunting for answers*
 
Old 06-11-2003, 04:49 AM   #10
kev82
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this is about the third time i have posted the same thing on this forum but nevermind. the output of a command can be captured by using popen() in stdio.h. its quite simple if you read the man pages.
 
Old 06-11-2003, 01:59 PM   #11
coolman0stress
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Excellent, thanks.
For some reason, most of my "programming buddies" didn't know how to do it.

Last edited by coolman0stress; 06-11-2003 at 02:02 PM.
 
  


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