How to Capture Real-time System Command Output in C/C using `popen`?

Capturing System Output with popen

Question:

How to effectively capture the real-time output of a system command invoked using system(), such as system("ls"), for further processing in C/C ?

Answer:

The popen function provides an efficient method for capturing output from system commands. Its syntax is:

#include <stdio.h>

FILE *popen(const char *command, const char *type);

int pclose(FILE *stream);

• command: Specifies the system command to execute.
• type: Indicates the mode to open the stream. Typically, use "r" for reading (stdout) or "w" for writing (stdin).

Process:

1. To open a stream for reading the command's output, use:

FILE *stream = popen(command, "r");

2. Read the stream as you would any other input source:

char buffer[1024];
while (fgets(buffer, sizeof(buffer), stream) != NULL) {
    // Process each line of output
}

3. Close the stream when done:

pclose(stream);

Example:

#include <stdio.h>

int main() {
    FILE *stream = popen("ls", "r");
    if (stream != NULL) {
        char buffer[1024];
        while (fgets(buffer, sizeof(buffer), stream) != NULL) {
            printf("%s", buffer);
        }
        pclose(stream);
    }
    return 0;
}

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