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Annotation of coherent/d/usr/src/examples/system.c, revision 1.1

1.1     ! root        1: #include <stdio.h>
        !             2: 
        !             3: FILE *newfp;
        !             4: int oldstdout;
        !             5: 
        !             6: main()
        !             7: {
        !             8:        extern int system();
        !             9: 
        !            10:        ropen("list.fil");
        !            11:        system("ls *.c");
        !            12:        rclose();
        !            13: }
        !            14: 
        !            15: /*
        !            16:  * Redirect stdout prior to system() call.
        !            17:  * You can't redirect child process's I/O
        !            18:  * but you can redirect main()'s and let the child inherit it.
        !            19:  */
        !            20: ropen(tofile)
        !            21: char *tofile;
        !            22: {
        !            23:        if ((newfp = fopen(tofile, "wr")) == NULL)
        !            24:                fatal("cannot open output file \"%s\"", tofile);
        !            25: 
        !            26:        /* Duplicate stdout so it can be restored later */
        !            27:        if ((oldstdout = dup(fileno(stdout))) == -1)
        !            28:                fatal("dup failed");
        !            29: 
        !            30:        /* Force duplication of new file handle as stdout */
        !            31:        if (dup2(fileno(newfp), fileno(stdout)) == -1)
        !            32:                fatal("dup2 failed");
        !            33: }
        !            34: 
        !            35: /*
        !            36:  * Terminate redirection
        !            37:  */
        !            38: rclose()
        !            39: {
        !            40:        /* Restore old stdout */
        !            41:        if (dup2(oldstdout, fileno(stdout)) == -1)
        !            42:                fatal("dup2 failed");
        !            43:        /* Close the extra handle */
        !            44:        if (close(oldstdout) != 0)
        !            45:                fatal("cannot close old stdout");
        !            46:        fclose(newfp);
        !            47: }
        !            48: 
        !            49: /*
        !            50:  * Fatal error
        !            51:  */
        !            52: fatal(p)
        !            53: char *p;
        !            54: {
        !            55:        fprintf(stderr, "system: %r\n", &p);
        !            56:        exit(1);
        !            57: }

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