　リダイレクション-2(fork,pipe,dup,execlp)

パイプにより，３つのプロセスの標準入出力を結ぶ例題です．

それぞれのパイプは，２つのパイプを作成してから２回 fork を行う方法により作成されています．

**リダイレクション-2(fork,pipe,dup,execlp)**(list_75.c)
#include <stdio.h> //----------------------------------------------------------------- // % man cat \| fold -w 60 \| tr a-z A-Z // --> cat のマニュアル内容を60文字で折り返し，小文字を大文字へ //----------------------------------------------------------------- int main() { int pfd1[2],pfd2[2]; int pid1,pid2,status; if(pipe(pfd1) < 0 \|\| pipe(pfd2) < 0){ perror("pipe"); exit(1); } if((pid1 = fork()) < 0){ perror("fork"); exit(1); } if(pid1 == 0){ // child close(pfd1[0]); close(1); dup2(pfd1[1],1); close(pfd1[1]); execlp("man","man","cat",NULL); } else { // parent close(pfd1[1]); close(0); dup2(pfd1[0],0); close(pfd1[0]); if((pid2 = fork()) < 0){ perror("fork"); exit(1); } if(pid2 == 0){ // child close(pfd2[0]); close(1); dup2(pfd2[1],1); close(pfd2[1]); execlp("fold","fold","-w","60",NULL); } else { close(pfd2[1]); close(0); dup2(pfd2[0],0); close(pfd2[0]); execlp("tr","tr","a-z","A-Z",NULL); } } return 0; }

リダイレクション-2(fork,pipe,dup,execlp)(list_75.c)

#include <stdio.h>

//-----------------------------------------------------------------
// % man cat | fold -w 60 | tr a-z A-Z
// --> cat のマニュアル内容を60文字で折り返し，小文字を大文字へ
//-----------------------------------------------------------------

int main()
{
    int pfd1[2],pfd2[2];
    int pid1,pid2,status;
    
    if(pipe(pfd1) < 0 || pipe(pfd2) < 0){
        perror("pipe");
        exit(1);
    }
    if((pid1 = fork()) < 0){
        perror("fork");
        exit(1);
    }

    if(pid1 == 0){ // child
        close(pfd1[0]);
        close(1);
        dup2(pfd1[1],1);
        close(pfd1[1]);
        execlp("man","man","cat",NULL);
    } else { // parent
        close(pfd1[1]);
        close(0);
        dup2(pfd1[0],0);
        close(pfd1[0]);
        if((pid2 = fork()) < 0){
            perror("fork");
            exit(1);
        }
        if(pid2 == 0){ // child
            close(pfd2[0]);
            close(1);
            dup2(pfd2[1],1);
            close(pfd2[1]);
            execlp("fold","fold","-w","60",NULL);
        } else {
            close(pfd2[1]);
            close(0);
            dup2(pfd2[0],0);
            close(pfd2[0]);
            execlp("tr","tr","a-z","A-Z",NULL);
        }
    }

    return 0;
}

実行結果

Gami[484]% ./list_76.exe CAT(1) USER COMMANDS CAT(1) NAME CAT - CONCATENATE FILES AND PRINT ON THE STANDARD OUT PUT SYNOPSIS CAT [OPTION] [FILE]... DESCRIPTION CONCATENATE FILE(S), OR STANDARD INPUT, TO STANDARD O UTPUT. -A, --SHOW-ALL EQUIVALENT TO -VET -B, --NUMBER-NONBLANK NUMBER NONBLANK OUTPUT LINES -E EQUIVALENT TO -VE -E, --SHOW-ENDS DISPLAY $ AT END OF EACH LINE -N, --NUMBER NUMBER ALL OUTPUT LINES -S, --SQUEEZE-BLANK NEVER MORE THAN ONE SINGLE BLANK LINE -T EQUIVALENT TO -VT -T, --SHOW-TABS DISPLAY TAB CHARACTERS AS ^I -U (IGNORED) -V, --SHOW-NONPRINTING USE ^ AND M- NOTATION, EXCEPT FOR LFD AND TAB --HELP DISPLAY THIS HELP AND EXIT --VERSION OUTPUT VERSION INFORMATION AND EXIT WITH NO FILE, OR WHEN FILE IS -, READ STANDARD INPUT. AUTHOR WRITTEN BY TORBJORN GRANLUND AND RICHARD M. STALLMAN. REPORTING BUGS REPORT BUGS TO . COPYRIGHT COPYRIGHT (C) 2004 FREE SOFTWARE FOUNDATION, INC. THIS IS FREE SOFTWARE; SEE THE SOURCE FOR COPYING C ONDITIONS. THERE IS NO WARRANTY; NOT EVEN FOR MERCHANTABILITY OR FITNE SS FOR A PARTICU- LAR PURPOSE. SEE ALSO THE FULL DOCUMENTATION FOR CAT IS MAINTAINED AS A TE XINFO MANUAL. IF THE INFO AND CAT PROGRAMS ARE PROPERLY INSTALLED AT YOUR SITE, THE COMMAND INFO COREUTILS CAT SHOULD GIVE YOU ACCESS TO THE COMPLETE MANUAL. CAT (COREUTILS) 5.2.1 MARCH 2004 CAT(1) Gami[485]%