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How to execute a command and save the results ??

Posted on 2004-05-03
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Last Modified: 2008-02-26
Simple:

I want to execute the command "ls" in my mandrake 10.

I have a variable "string command;", so I want that "command" gets the result of the "ls" command.

Something like this:

string command;  // Variable
command = // Whatever is under "ls"
cout << command; // This should print home  folders  etc...
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Comment
Question by:digi_mind
6 Comments
 
LVL 12

Expert Comment

by:stefan73
ID: 10978770
Hi digi_mind,
What you're looking for is the popen command:

#include <stdio.h>

FILE* ls_output = popen("ls", "r");
[...]
pclose(ls_output);

...but unfortunately, this uses C-style, buffered IO. I'm not sure if there is a constructor for an istream which takes a FILE* as argument. Try it out.

Cheers,
Stefan
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LVL 12

Accepted Solution

by:
stefan73 earned 100 total points
ID: 10978899
Try this:

#include <stdio.h>

main(){
    char buffer[1024];
    string command;
    size_t chars;

    FILE* ls_output = popen("ls", "r");
    while(chars = fread(buffer,1,sizeof(buffer),ls_output))
        command.append(buffer,chars);    

    pclose(ls_output);

    cout << command;

}
0
 

Author Comment

by:digi_mind
ID: 10984364
I have this to execute a specific command in Linux

#include <stdio.h>

main(){
    char buffer[1024];
    string command;
    size_t chars;

    FILE* ls_output = popen("ls", "r");
    while(chars = fread(buffer,1,sizeof(buffer),ls_output))
        command.append(buffer,chars);    

    pclose(ls_output);

    cout << command;

}

what can I do to execute any command not only the one I specify, for example I have in a string called request command, which contains any command that a user types, I want that command to be executed and the result displayed.
How can I do that ?
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LVL 35

Assisted Solution

by:Duncan Roe
Duncan Roe earned 100 total points
ID: 10984906
Cheap & cheerful solution:
Pass the command in quotes, e.g.:-
myprog "ls -A -Fx"

Now change your above program line 8 to be 'FILE* ls_output = popen(argv[1], "r");'
0
 

Author Comment

by:digi_mind
ID: 10984965
Ok, I will try to ask in a simplier way:

This is my program:
*******************
string command;
cin >> command;
FILE * test = popen(command , "r");
***********************************
This does not work... and I do not know why. Any suggestion ???

0
 
LVL 1

Expert Comment

by:arn0ld
ID: 10992114
how about a
 cout<<command<<endl;
after cin?

You are calling  MyProgram as
echo ls|MyProgram
not as
MyProgram ls  
?
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