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Save system() into char[]

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# 1  
Old 04-12-2012
Save system() into char[]
Hi!
I have something like this :
Code:
...
char buffer[25] = "ls -l";
system(buffer);
...

and i just want to save what i get to the terminal from ls -l into a char.
I first think of doing something like ls -l>text.txt and after opening the file in my program and fscanf(). Any faster way ?
Smilie
Last edited by giampoul; 04-12-2012 at 10:13 AM..
# 2  
Old 04-12-2012
Code:
char buf[512];
FILE *fp=popen("ls -l", "r");

while(fgets(fp, 512, fp))
{
...
}

pclose(fp);

This User Gave Thanks to Corona688 For This Post:
giampoul
# 3  
Old 04-12-2012
Quote:
Originally Posted by Corona688
Code:
char buf[512];
FILE *fp=popen("ls -l", "r");

while(fgets(fp, 512, fp))
{
...
}

pclose(fp);

Thanks! I used this code :
Code:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main()
{
	char str[20] = "ls -l text.txt";
	FILE *fp;
	int status;
	char terminal[512];
	
	fp = popen(str, "r");
	if( fp == NULL )
	{
		printf("popen error\n");
		exit(EXIT_FAILURE);
	}
	fgets(terminal, 512, fp);
	status = pclose(fp);
	if( status == -1 )
	{
		printf("pclose error\n");
		exit(EXIT_FAILURE);
	}
	printf("Terminal will give this:\n%s", terminal);
}

and it gives me what i wanted...
I didnt understand in your example the while loop use...
But this works! Thanks!
# 4  
Old 04-12-2012
Quote:
Originally Posted by giampoul
I didnt understand in your example the while loop use...
Because it's completely possible for a program to print more than one line. Smilie fgets() just reads the lines one at a time. Inside the loop, you can use the contents of the line as you see fit.

The loop breaks when it hits EOF because fgets() will return null if it's unable to read a line, which if/while/etc will consider to be a false value.

In the end I suppose it doesn't matter, but I've made it a habit to read until EOF so the program you're reading from can quit cleanly instead of getting killed by sigpipe.
Last edited by Corona688; 04-12-2012 at 01:58 PM..
This User Gave Thanks to Corona688 For This Post:
giampoul
# 5  
Old 04-16-2012
don't forget to use W macros (WEXITSTATUS , etc...) when checking return status of pclose
This User Gave Thanks to migurus For This Post:
giampoul
# 6  
Old 04-18-2012
Quote:
Originally Posted by migurus
don't forget to use W macros (WEXITSTATUS , etc...) when checking return status of pclose
A little more about this? Maybe an example? Smilie
# 7  
Old 04-18-2012
These macros are used to check process status. The pclose() call does report exit status of the process which has been run by corresponding popen().

Code:
int rc;
rc = pclose(pfp);
printf("rc=%i\n", WEXITSTATUS(rc));

Just bear in mind when examine a return code of a command, make sure IF there is a wrapper shell that executes the program which code you expect to see, then the wrapper needs to store your program's exit code and return it.
This User Gave Thanks to migurus For This Post:
giampoul
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