4 ms·

This is not the first time popen with | has led to security issues. At the same time it doesn't have any legitimate use cases that I can think of. Is there any

• MereInterest 10y ago
  It can be useful if you want to offload some of the processing to other processes. // Open a gzipped file, display progress bar snprintf(buf, sizeof(buf), "pv %s | zcat", filename); FILE* f = popen(buf, "r"); // Add an additional processing step when reading file FILE* f = NULL; if(do_extra_step) { snprintf(buf, sizeof(buf), "zcat %s | extra_step", filename); f = popen(buf, "r"); } else { snprintf(buf, sizeof(buf), "zcat %s", filename); f = popen(buf, "r"); } The first example could be replicated by using zlib and reproducing pv's progress bar in-app. More work, but nothing especially tricky about it. For the second example, it would be more difficult, for two reasons. First, popen() can open either a read or a write pipe, but not both. In order to write to extra_step's stdin, then read from stdout, you'll need to switch over to fork/exec. Second, you'll have to handle all the buffering between zcat and extra_step yourself, rather than getting it for free.