Does fprintf() work for writing in a pipe, or I must always use write()?

Question

Keep in mind that when using fprintf() I'm aware that I need to pass the file descriptor for writing to the pipe. I just have the doubt and wish to know right now; I don't really have any kind of sample code.

In addition, I want to know if functions such as fputc(), fputs() will also work.

Answer 1

Using fprintf() requires a file stream ( FILE * ). When you create a pipe, you get two file descriptors. File descriptors are not the same as streams.

You can use the POSIX fdopen() function to create a file stream from a file descriptor; you can then use fprintf() on that file stream — or any of the other standard I/O functions that take an explicit file stream argument and write to the stream. You can't use fseek() ; you'll get an error ( ESPIPE — illegal seek).

You can (in theory) use the POSIX dprintf() function to write directly to a file descriptor — if your system supports it.

Answer 2

You can use fdopen() to convert a file descriptor to a FILE * , and then use all the stdio functions.

int pipefd[2];
pipe(pipefd);

FILE *pipeout = fdopen(pipefd[1], "w");
fprintf(pipeout, "Message written to the pipe\n");