在管道上使用fgets（）

Question

I need to write program, which work on Linux OS:

• when the main program starts, a child program separates from main program and child can be executed when it gets an interruption from parent program;

• parent program waits for a text line, enetered from keyboard (text line should end by pressing );

• after the text line is entered, parent program sends an interruption to child program, which reads the text line trough "Pipe" channel and creates a text file with it.

• if an empty line is entered, then both parts of the program end their work.

The problem is, I know that it is bad to use gets(), so how can I use fgets() instead in my case?

 #include <stdio.h>
 #include <stdlib.h>
 #include <errno.h>
 #include <sys/types.h>
 #include <unistd.h>

 FILE *f;

 int main(void)
 {
 int pfds[2];
 char buf[1000];

 pipe(pfds);
 f = fopen("input.txt", "w");
 fclose(f);


do 
{

    if (!fork()) 
    {
     printf("PARENT: enter input text from keyboard\n");
     gets(buf);
         printf("PARENT: writing to the pipe\n");
         write(pfds[1], buf, 1000);
     printf("PARENT: exiting\n");
         exit(0);
     } 
     else 
    {
     f = fopen("input.txt", "a+");
         printf("CHILD: waiting from PARENT\n");
         read(pfds[0], buf, 1000);
     printf("CHILD: read \"%s\"\n", buf);        
     fprintf(f,"%s\n", buf);
     fclose(f);
     printf("CHILD: input.txt file created\n", buf);
         wait(NULL);
     }
 } 
     while (buf[0] != '\0');

     printf("PROGRAM: done\n");

     return 0;
 }

Answer 1

You have opened file in "w" mode.

f = fopen("program.txt", "w");

w mode creates an empty file for writing. If a file with the same name already exists, its content is erased and the file is considered as a new empty file.

Open the file in "w+" or "a+" mode.