Practical C Programs

Command Router

Command-line style programs often map a selected command to one compact action path.

command choice The program turns a small integer choice into a command name and status code.
routing Branches keep each command path explicit while sharing the same final reporting step.

Command Router

commandChoice
command_router.c
Replay: real traced execution (multi-file project)
#include <stdio.h>

int main(void) {
    int commandChoice = 1;
    const char *command = "build";
    int status = 0;

    if (commandChoice == 0) {
        command = "test";
        status = 0;
    } else if (commandChoice == 2) {
        command = "deploy";
        status = 2;
    }

    printf("choice=%d command=%s status=%d\n", commandChoice, command, status);
    return 0;
}

#include <stdio.h>

int main(void) {
    int commandChoice = 0;
    const char *command = "build";
    int status = 0;

    if (commandChoice == 0) {
        command = "test";
        status = 0;
    } else if (commandChoice == 2) {
        command = "deploy";
        status = 2;
    }

    printf("choice=%d command=%s status=%d\n", commandChoice, command, status);
    return 0;
}

#include <stdio.h>

int main(void) {
    int commandChoice = 2;
    const char *command = "build";
    int status = 0;

    if (commandChoice == 0) {
        command = "test";
        status = 0;
    } else if (commandChoice == 2) {
        command = "deploy";
        status = 2;
    }

    printf("choice=%d command=%s status=%d\n", commandChoice, command, status);
    return 0;
}

  1. commandChoice ← 1, command ← build, status ← 0

    3int main(void) {4    int commandChoice→ 1 = 1; //@commandChoice=0, 25    const char *command→ build = "build";6    int status→ 0 = 0;78    if (commandChoice == 0) {9        command = "test";10        status = 0;11    } else if (commandChoice == 2) {12        command = "deploy";13        status = 2;14    }1516    printf("choice=%d command=%s status=%d\n", commandChoice1, commandbuild, status0);17    return 0;18}
    outputchoice=1 command=build status=0

  1. commandChoice ← 0, command ← build, status ← 0

    3int main(void) {4    int commandChoice→ 0 = 0;5    const char *command→ build = "build";6    int status→ 0 = 0;

  2. command ← test

    8if (commandChoice0 == 0) {9    command→ test = "test";10    status0 = 0;11} else if (commandChoice == 2) {

  3. printf("choice=%d command=%s status=%d ", commandChoice, command, stat…

    16    printf("choice=%d command=%s status=%d\n", commandChoice0, commandtest, status0);17    return 0;18}
    outputchoice=0 command=test status=0

  1. commandChoice ← 2, command ← build, status ← 0

    3int main(void) {4    int commandChoice→ 2 = 2;5    const char *command→ build = "build";6    int status→ 0 = 0;

  2. command ← deploy, status ← 2

    10    status = 0;11} else if (commandChoice2 == 2) {12    command→ deploy = "deploy";13    status→ 2 = 2;14}

  3. printf("choice=%d command=%s status=%d ", commandChoice, command, stat…

    16    printf("choice=%d command=%s status=%d\n", commandChoice2, commanddeploy, status2);17    return 0;18}
    outputchoice=2 command=deploy status=2