CODEWITHSUNDEEP
clinuxunixawkredhat
Matthew Hoggan
Matthew Hoggan

Reputation: 7594

Advance Programming in the Unix Environment: Get Configuration Limits Figure 2.12 "Build C Program to print all supported configuration limits"

The author claims that his awk script will print out all the limits for a POSIX.1 and XSI compliant system. I am using Red Hat Enterprise Linux Server release 6.0 (Santiago). When I run his awk script it does not seem to be printing out the #ifdef portion of the C program. My thoughts are that sysconf.sym do not exist on this distribution, therefore the while loops never run. Could someone please confirm that? If this is the case what changes would I need to make to the awk script to get it to print out the #ifdef portion of the code? The awk script is:

# Run with awk -f <awk_script>

BEGIN   {
    printf("#include \"apue.h\"\n")
    printf("#include <errno.h>\n")
    printf("#include <limits.h>\n")
    printf("#include <stdio.h>\n")
    printf("\n")

    printf("int log_to_stderr = 0;\n")

    printf("static void pr_sysconf(char *, int);\n")
    printf("static void pr_pathconf(char *, char *, int);\n")
    printf("\n")
    printf("int\n")
    printf("main(int argc, char *argv[])\n")
    printf("{\n")
    printf(" if (argc != 2)\n")
    printf("  err_quit(\"usage: a.out <dirname>\");\n\n")
    FS="\t+"
    while (getline <"sysconf.sym" > 0) {
        printf("#ifdef %s\n", $1)
        printf(" printf(\"%s defined to be %%d\\n\", %s+0);\n", $1, $1)
        printf("#else\n")
        printf(" printf(\"no symbol for %s\\n\");\n", $1)
        printf("#endif\n")
        printf("#ifdef %s\n", $2)
        printf(" pr_sysconf(\"%s =\", %s);\n", $1, $2)
        printf("#else\n")
        printf(" printf(\"no symbol for %s\\n\");\n", $2)
        printf("#endif\n")
    }
    close("sysconf.sym")
    while (getline <"pathconf.sym" > 0) {
        printf("#ifdef %s\n", $1)
        printf(" printf(\"%s defined to be %%d\\n\", %s+0);\n", $1, $1)
        printf("#else\n")
        printf(" printf(\"no symbol for %s\\n\");\n", $1)
        printf("#endif\n")
        printf("#ifdef %s\n", $2)
        printf(" pr_pathconf(\"%s =\", argv[1], %s);\n", $1, $2)
        printf("#else\n")
        printf(" printf(\"no symbol for %s\\n\");\n", $2)
        printf("#endif\n")
    }
    close("pathconf.sym")
    exit
}
END {
    printf(" exit(0);\n")
    printf("}\n\n")
    printf("static void\n")
    printf("pr_sysconf(char *mesg, int name)\n")
    printf("{\n")
    printf(" long val;\n\n")
    printf(" fputs(mesg, stdout);\n")
    printf(" errno = 0;\n")
    printf(" if ((val = sysconf(name)) < 0) {\n")
    printf("  if (errno != 0) {\n")
    printf("   if (errno == EINVAL)\n")
    printf("    fputs(\" (not supported)\\n\", stdout);\n")
    printf("   else\n")
    printf("    err_sys(\"sysconf error\");\n")
    printf("  } else {\n")
    printf("   fputs(\" (no limit)\\n\", stdout);\n")
    printf("  }\n")
    printf(" } else {\n")
    printf("  printf(\" %%ld\\n\", val);\n")
    printf(" }\n")
    printf("}\n\n")
    printf("static void\n")
    printf("pr_pathconf(char *mesg, char *path, int name)\n")
    printf("{\n")
    printf(" long val;\n")
    printf("\n")
    printf(" fputs(mesg, stdout);\n")
    printf(" errno = 0;\n")
    printf(" if ((val = pathconf(path, name)) < 0) {\n")
    printf("  if (errno != 0) {\n")
    printf("   if (errno == EINVAL)\n")
    printf("    fputs(\" (not supported)\\n\", stdout);\n")
    printf("   else\n")
    printf("    err_sys(\"pathconf error, path = %%s\", path);\n")
    printf("  } else {\n")
    printf("   fputs(\" (no limit)\\n\", stdout);\n")
    printf("  }\n")
    printf(" } else {\n")
    printf("  printf(\" %%ld\\n\", val);\n")
    printf(" }\n")
    printf("}\n")
}

Update

If you would like the apue.h header so you can compile the C program that can be found at. apue.h

Upvotes: 2

Views: 599

Answers (3)

jim mcnamara
jim mcnamara

Reputation: 16389

I think Rago mentions getconf in the 2nd Edtion of APUE. Aside from losing the fun of debugging the awk, code it is meant to serve the purpose you require, and do it portably.

Check out:

http://pubs.opengroup.org/onlinepubs/009604599/utilities/getconf.html

Upvotes: 1

Robᵩ
Robᵩ

Reputation: 168716

You need to download the files from here: http://www.apuebook.com/sourcecode.html

Upvotes: 1

D.Shawley
D.Shawley

Reputation: 59583

I believe that sysconf.sym and pathconf.sym had to be written or were supplied on disk or something. It's been a while since I read APUE.

Update: google turned up the following link http://www.cs.karelia.ru/~vadim/sp2009/apue.2e/std/

Upvotes: 2

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