CODEWITHSUNDEEP
clinuxfile-io
henryyao
henryyao

Reputation: 1818

what does "output popen() streams are fully bufered by default" mean?

According to man popen, "output popen() streams are fully bufered by default". But for the following code, i can still get all the information of my ls -l command, without the fflush(p) command. Does that make sence? I thought I would need the fflush(p) to flush the command's output that are stored in the user buffer, to the std out.

#include <stdio.h>

int main()
{
   FILE *p=popen("ls -l","r");
   char buf[100];
   memset(buf,0x00,100);
   //fflush(p);

   fread(buf,sizeof(char),90,p);

   printf("%s",buf);
   pclose(p);

   return 0;
}

Upvotes: 0

Views: 109

Answers (1)

Dietrich Epp
Dietrich Epp

Reputation: 213338

That's an input popen() stream, not an output stream.

The fflush() function only operates on output or update streams, not input streams.

Upvotes: 3

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