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











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












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






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























    Your Answer






    StackExchange.ifUsing("editor", function () {
    StackExchange.using("externalEditor", function () {
    StackExchange.using("snippets", function () {
    StackExchange.snippets.init();
    });
    });
    }, "code-snippets");

    StackExchange.ready(function() {
    var channelOptions = {
    tags: "".split(" "),
    id: "1"
    };
    initTagRenderer("".split(" "), "".split(" "), channelOptions);

    StackExchange.using("externalEditor", function() {
    // Have to fire editor after snippets, if snippets enabled
    if (StackExchange.settings.snippets.snippetsEnabled) {
    StackExchange.using("snippets", function() {
    createEditor();
    });
    }
    else {
    createEditor();
    }
    });

    function createEditor() {
    StackExchange.prepareEditor({
    heartbeatType: 'answer',
    convertImagesToLinks: true,
    noModals: true,
    showLowRepImageUploadWarning: true,
    reputationToPostImages: 10,
    bindNavPrevention: true,
    postfix: "",
    imageUploader: {
    brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
    contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
    allowUrls: true
    },
    onDemand: true,
    discardSelector: ".discard-answer"
    ,immediatelyShowMarkdownHelp:true
    });


    }
    });














     

    draft saved


    draft discarded


















    StackExchange.ready(
    function () {
    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53420606%2fpassing-integers-in-place-of-file-descriptor-when-calling-write-command-in-c%23new-answer', 'question_page');
    }
    );

    Post as a guest















    Required, but never shown

























    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






























             

            draft saved


            draft discarded



















































             


            draft saved


            draft discarded














            StackExchange.ready(
            function () {
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53420606%2fpassing-integers-in-place-of-file-descriptor-when-calling-write-command-in-c%23new-answer', 'question_page');
            }
            );

            Post as a guest















            Required, but never shown





















































            Required, but never shown














            Required, but never shown












            Required, but never shown







            Required, but never shown

































            Required, but never shown














            Required, but never shown












            Required, but never shown







            Required, but never shown







            -

            Popular posts from this blog

            Trompette piccolo

            Image
            Ne doit pas être confondu avec trompette de poche. Trompette piccolo en si bémol, avec des branches d'embouchure différentes pour le si bémol (la plus courte) ou la (la plus longue) Trompette piccolo La trompette piccolo est la plus petite de la famille des trompettes. Elle joue une octave plus haut que la trompette standard en si bémol. La plupart des trompettes piccolo sont conçues pour jouer dans les deux tonalités de si bémol ou la, en utilisant une branche d'embouchure différente pour chaque tonalité. Le tube de la trompette piccolo en si bémol a une longueur moitié de celle de la trompette normale en si bémol. Des trompettes piccolo en sol, fa, ut sont également fabriquées, mais elles sont rares. La trompette soprano en ré, aussi connu comme la « trompette Bach », a été inventée vers 1890 par le facteur belge Victor-Charles Mahillon pour jouer les parties hautes de la trompette dans la musique de Bach et Haendel. La trompette piccolo moderne permet aux
            Read more

            How do I get these specific pathlines to nodes?

            Image
            2 I have four nodes, one parent and three children. I am trying to link with these specific arrow paths: I have only just started working with the tikz package and my code so far looks like: usepackage{tikz} usetikzlibrary{arrows,positioning,calc} begin{document} begin{tikzpicture}[ ,node distance =5mm ,>=latex' ,block/.style ={ ,draw ,minimum height = 10mm ,minimum width =28mm ,align=center } ,every path/.style={->} %sets arrow style ] node [block] (main) {Main}; node [block, below=of main] (second) {Second}; node [block, left=of second] (first) {First}; node [block, right=of second] (third) {Third}; draw (main) to (first); draw (main) to (second); draw (main) to (third); end{tikzpicture} end{document} Which gives me: I tried using -| but that
            Read more

            What visual should I use to simply compare current year value vs last year in Power BI desktop

            Image
            0 I have column SubToBind that shows current year ratio and column PY SubToBind which shows previous year ratio. How can I simply create a card that would be displaying them both in a nice way? Something like that: I cannot achieve that with regular card, I also tried Card with States by OKViz but also unable to see both values. In KPI visual - I dont like the word "Goal", it will confuse end users. Are there any cards or other visuals that would do the job? Thanks powerbi dax powerbi-embedded share | improve this question edited Jun 11 '18 at 20:11 Oleg
            Read more