passing integers in place of file descriptor when calling write command in c











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0
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void main()

{



     pid_t  pid;

     int    i;

     char   buf[BUF_SIZE];

     fork();

     pid = getpid();

     for (i = 1; i <= MAX_COUNT; i++) {

          sprintf(buf, "This line is from pid %d, value = %dn", pid, i);

          write(1, buf, strlen(buf));

        // printf("%s",buf);

     }

}


I've got the given simple code to show fork process in c. I noticed that when I pass any value greater than 2 in place of 1 in write command the code does not print anything. Why is this happening?






c







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  • 2




    You should check the return value of write for an error.
    – Fiddling Bits
    Nov 21 at 21:20










  • 1 is for standard output descriptor, 2 is for error. Others aren't open
    – Jean-François Fabre
    Nov 21 at 21:24










  • note that the fork part is irrelevant to the question. The example could be reduced even more to only include a write call.
    – Jean-François Fabre
    Nov 21 at 21:31















up vote
0
down vote

favorite












void main()

{



     pid_t  pid;

     int    i;

     char   buf[BUF_SIZE];

     fork();

     pid = getpid();

     for (i = 1; i <= MAX_COUNT; i++) {

          sprintf(buf, "This line is from pid %d, value = %dn", pid, i);

          write(1, buf, strlen(buf));

        // printf("%s",buf);

     }

}


I've got the given simple code to show fork process in c. I noticed that when I pass any value greater than 2 in place of 1 in write command the code does not print anything. Why is this happening?






c







share|improve this question




















  • 2




    You should check the return value of write for an error.
    – Fiddling Bits
    Nov 21 at 21:20










  • 1 is for standard output descriptor, 2 is for error. Others aren't open
    – Jean-François Fabre
    Nov 21 at 21:24










  • note that the fork part is irrelevant to the question. The example could be reduced even more to only include a write call.
    – Jean-François Fabre
    Nov 21 at 21:31













up vote
0
down vote

favorite









up vote
0
down vote

favorite











void main()

{



     pid_t  pid;

     int    i;

     char   buf[BUF_SIZE];

     fork();

     pid = getpid();

     for (i = 1; i <= MAX_COUNT; i++) {

          sprintf(buf, "This line is from pid %d, value = %dn", pid, i);

          write(1, buf, strlen(buf));

        // printf("%s",buf);

     }

}


I've got the given simple code to show fork process in c. I noticed that when I pass any value greater than 2 in place of 1 in write command the code does not print anything. Why is this happening?






c







share|improve this question















void main()

{



     pid_t  pid;

     int    i;

     char   buf[BUF_SIZE];

     fork();

     pid = getpid();

     for (i = 1; i <= MAX_COUNT; i++) {

          sprintf(buf, "This line is from pid %d, value = %dn", pid, i);

          write(1, buf, strlen(buf));

        // printf("%s",buf);

     }

}


I've got the given simple code to show fork process in c. I noticed that when I pass any value greater than 2 in place of 1 in write command the code does not print anything. Why is this happening?






c




c






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 21 at 21:22









NathanOliver

83k15112173




83k15112173










asked Nov 21 at 21:19









Ashray Sinha

51




51








  • 2




    You should check the return value of write for an error.
    – Fiddling Bits
    Nov 21 at 21:20










  • 1 is for standard output descriptor, 2 is for error. Others aren't open
    – Jean-François Fabre
    Nov 21 at 21:24










  • note that the fork part is irrelevant to the question. The example could be reduced even more to only include a write call.
    – Jean-François Fabre
    Nov 21 at 21:31














  • 2




    You should check the return value of write for an error.
    – Fiddling Bits
    Nov 21 at 21:20










  • 1 is for standard output descriptor, 2 is for error. Others aren't open
    – Jean-François Fabre
    Nov 21 at 21:24










  • note that the fork part is irrelevant to the question. The example could be reduced even more to only include a write call.
    – Jean-François Fabre
    Nov 21 at 21:31








2




2




You should check the return value of write for an error.
– Fiddling Bits
Nov 21 at 21:20




You should check the return value of write for an error.
– Fiddling Bits
Nov 21 at 21:20












1 is for standard output descriptor, 2 is for error. Others aren't open
– Jean-François Fabre
Nov 21 at 21:24




1 is for standard output descriptor, 2 is for error. Others aren't open
– Jean-François Fabre
Nov 21 at 21:24












note that the fork part is irrelevant to the question. The example could be reduced even more to only include a write call.
– Jean-François Fabre
Nov 21 at 21:31




note that the fork part is irrelevant to the question. The example could be reduced even more to only include a write call.
– Jean-François Fabre
Nov 21 at 21:31












1 Answer
1






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oldest

votes

















up vote
1
down vote



accepted










you're performing a raw write call where at the start of your program:




  • 1 is the standard output descriptor

  • 2 is the standard error descriptor


Both write to the console by default (and 0 is the standard input, cannot be written to)



Other descriptors are invalid unless they've been returned by an open call. Since you don't check the return value of write, you can't see that an error code is returned (probably EBADF, bad file descriptor)






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    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    1
    down vote



    accepted










    you're performing a raw write call where at the start of your program:




    • 1 is the standard output descriptor

    • 2 is the standard error descriptor


    Both write to the console by default (and 0 is the standard input, cannot be written to)



    Other descriptors are invalid unless they've been returned by an open call. Since you don't check the return value of write, you can't see that an error code is returned (probably EBADF, bad file descriptor)






    share|improve this answer



























      up vote
      1
      down vote



      accepted










      you're performing a raw write call where at the start of your program:




      • 1 is the standard output descriptor

      • 2 is the standard error descriptor


      Both write to the console by default (and 0 is the standard input, cannot be written to)



      Other descriptors are invalid unless they've been returned by an open call. Since you don't check the return value of write, you can't see that an error code is returned (probably EBADF, bad file descriptor)






      share|improve this answer

























        up vote
        1
        down vote



        accepted







        up vote
        1
        down vote



        accepted






        you're performing a raw write call where at the start of your program:




        • 1 is the standard output descriptor

        • 2 is the standard error descriptor


        Both write to the console by default (and 0 is the standard input, cannot be written to)



        Other descriptors are invalid unless they've been returned by an open call. Since you don't check the return value of write, you can't see that an error code is returned (probably EBADF, bad file descriptor)






        share|improve this answer














        you're performing a raw write call where at the start of your program:




        • 1 is the standard output descriptor

        • 2 is the standard error descriptor


        Both write to the console by default (and 0 is the standard input, cannot be written to)



        Other descriptors are invalid unless they've been returned by an open call. Since you don't check the return value of write, you can't see that an error code is returned (probably EBADF, bad file descriptor)







        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited Nov 21 at 21:30

























        answered Nov 21 at 21:25









        Jean-François Fabre

        97.9k950107




        97.9k950107






























             

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