how to store the output of system() call?

Question

I am using system(3) on Linux in c++ programs. Now I need to store the output of system(3) in an array or sequence. How I can store the output of system(3).

I am using following:

system("grep -A1 \"<weakObject>\" file_name | grep \"name\" |
    grep -Po \"xoc.[^<]*\" | cut -d \".\" -f5 ");  

which gives output:

changin 
fdjgjkds 
dglfvk
dxkfjl

I need to store this output to an array of strings or Sequence of string.

Thanks in advance

Answer 1

You should use popen to read the command output from stdin. so, you'd do something like:

FILE *pPipe;
pPipe = popen("grep -A1 \"\" file_name | grep \"name\" | grep -Po \"xoc.[^<]*\" | cut -d \".\" -f5 ", "rt")

to open it in read text mode and then use fgets or something similar to read from the pipe:

fgets(psBuffer, 128, pPipe)

Answer 2

The esier way:

std::stringstream  result_stream;
std::streambuf     *backup  = std::cout.rdbuf( result_stream.rdbuf() );

int res = system("grep -A1 \"<weakObject>\" file_name | grep \"name\" |
grep -Po \"xoc.[^<]*\" | cut -d \".\" -f5 ");

std::cout.rdbuf(backup);

std::cout << result_stream.str();

Answer 3

system spawns a new shell process that isn't connected to the parent through a pipe or something else.

You need to use the popen library function instead. Then read the output and push each string into your array as you encounter newline characters.

FILE *fp = popen("grep -A1 \"<weakObject>\" file_name | grep \"name\" |
grep -Po \"xoc.[^<]*\" | cut -d \".\" -f5 ", "r");
char buf[1024];

while (fgets(buf, 1024, fp)) {
  /* do something with buf */
}

fclose(fp);