[Bash'изм] Своя программа в конвеере.

while read str
do
    echo $str\n
done > file

#include "stdio.h"

int main()
{
  char buf[256];
  while (!feof(stdin))
  {
    fgets(buf, 256, stdin);
    printf("<<<<%s", buf);
  }
}

> cat pipe_test.c| ./a.out                                                                                                                                                                ~ 
<<<<#include "stdio.h"                                                                                                                                                                      
<<<<                                                                                                                                                                                        
<<<<int main()                                                                                                                                                                              
<<<<{                                                                                                                                                                                       
<<<<  char buf[256];                                                                                                                                                                        
<<<<  while (!feof(stdin))                                                                                                                                                                  
<<<<  {                                                                                                                                                                                     
<<<<    fgets(buf, 256, stdin);                                                                                                                                                             
<<<<    printf("<<<<%s", buf);                                                                                                                                                              
<<<<  }                                                                                                                                                                                     
<<<<}                                                                                                                                                                                       
<<<<}  

FILE *out;
out = fopen, blablabla
char c;
while (!feof(stdin)) {
      c = fgetc(stdin);
      fputc(out, c);
}
fcole(out);