C: الإدخال/الإخراج المتقدم وسطر الأوامر

int main(int argc, char *argv[])

#include <stdio.h>

int main(int argc, char *argv[]) {
    printf("Argument count: %d\n", argc);
    for (int i = 0; i < argc; i++) {
        printf("argv[%d] = %s\n", i, argv[i]);
    }
    return 0;
}

./program hello world 123

Argument count: 4
argv[0] = ./program
argv[1] = hello
argv[2] = world
argv[3] = 123

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char *argv[]) {
    int verbose = 0;
    int count = 1;
    const char *filename = NULL;

    for (int i = 1; i < argc; i++) {
        if (strcmp(argv[i], "-v") == 0 || strcmp(argv[i], "--verbose") == 0) {
            verbose = 1;
        } else if (strcmp(argv[i], "-n") == 0 && i + 1 < argc) {
            count = atoi(argv[++i]);
        } else if (argv[i][0] != '-') {
            filename = argv[i];
        } else {
            fprintf(stderr, "Unknown option: %s\n", argv[i]);
            return 1;
        }
    }

    if (filename == NULL) {
        fprintf(stderr, "Usage: %s [-v] [-n count] filename\n", argv[0]);
        return 1;
    }

    printf("File: %s, Count: %d, Verbose: %s\n",
           filename, count, verbose ? "on" : "off");
    return 0;
}

char *getenv(const char *name);

#include <stdio.h>
#include <stdlib.h>

int main(void) {
    const char *path = getenv("PATH");
    if (path != NULL) {
        printf("PATH = %s\n", path);
    }

    const char *home = getenv("HOME");
    if (home != NULL) {
        printf("HOME = %s\n", home);
    }
    return 0;
}

#include <stdio.h>

extern char **environ;

int main(void) {
    char **env = environ;
    while (*env) {
        printf("%s\n", *env);
        env++;
    }
    return 0;
}

#include <errno.h>

void perror(const char *s);
char *strerror(int errnum);

#include <stdio.h>
#include <errno.h>
#include <string.h>

int main(void) {
    FILE *fp = fopen("nonexistent_file.txt", "r");
    if (fp == NULL) {
        perror("fopen");
        printf("Error code: %d, Error message: %s\n", errno, strerror(errno));
        return 1;
    }
    fclose(fp);
    return 0;
}

fopen: No such file or directory
Error code: 2, Error message: No such file or directory

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>

int main(int argc, char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s filename\n", argv[0]);
        return 1;
    }

    FILE *fp = fopen(argv[1], "r");
    if (fp == NULL) {
        fprintf(stderr, "Cannot open '%s': %s\n", argv[1], strerror(errno));
        return 1;
    }

    int ch;
    while ((ch = fgetc(fp)) != EOF) {
        putchar(ch);
    }

    if (ferror(fp)) {
        fprintf(stderr, "Read error occurred: %s\n", strerror(errno));
        fclose(fp);
        return 1;
    }

    fclose(fp);
    return 0;
}

#include <stdio.h>

int main(void) {
    fprintf(stdout, "This is normal output\n");
    fprintf(stderr, "This is error output\n");
    return 0;
}

./program > output.txt

./program 2>&1 all.log

FILE *tmpfile(void);

#include <stdio.h>

int main(void) {
    FILE *tmp = tmpfile();
    if (tmp == NULL) {
        perror("tmpfile");
        return 1;
    }

    fprintf(tmp, "Temporary data %d\n", 42);
    rewind(tmp);

    char buf[64];
    while (fgets(buf, sizeof(buf), tmp) != NULL) {
        printf("%s", buf);
    }

    fclose(tmp);
    return 0;
}

Temporary data 42

char *tmpnam(char *s);

#include <stdio.h>
#include <string.h>

int main(void) {
    FILE *tmp = tmpfile();
    if (tmp == NULL) {
        perror("tmpfile");
        return 1;
    }

    char *lines[] = {"banana", "apple", "orange", "grape"};
    int n = 4;

    for (int i = 0; i < n; i++) {
        fprintf(tmp, "%s\n", lines[i]);
    }

    rewind(tmp);
    printf("Before sorting:\n");
    char buf[64];
    while (fgets(buf, sizeof(buf), tmp) != NULL) {
        buf[strcspn(buf, "\n")] = '\0';
        printf("  %s\n", buf);
    }

    rewind(tmp);
    for (int i = 0; i < n - 1; i++) {
        for (int j = 0; j < n - 1 - i; j++) {
            char a[64], b[64];
            long pos = ftell(tmp);
            fgets(a, sizeof(a), tmp);
            fgets(b, sizeof(b), tmp);
            a[strcspn(a, "\n")] = '\0';
            b[strcspn(b, "\n")] = '\0';

            if (strcmp(a, b) > 0) {
                fseek(tmp, pos, SEEK_SET);
                fprintf(tmp, "%s\n%s\n", b, a);
            } else {
                fseek(tmp, pos, SEEK_SET);
                fprintf(tmp, "%s\n%s\n", a, b);
            }
            fseek(tmp, pos + strlen(a) + strlen(b) + 2, SEEK_SET);
        }
        rewind(tmp);
    }

    rewind(tmp);
    printf("After sorting:\n");
    while (fgets(buf, sizeof(buf), tmp) != NULL) {
        buf[strcspn(buf, "\n")] = '\0';
        printf("  %s\n", buf);
    }

    fclose(tmp);
    return 0;
}

Before sorting:
  banana
  apple
  orange
  grape
After sorting:
  apple
  grape
  orange
  banana

int snprintf(char *str, size_t size, const char *format, ...);

#include <stdio.h>

int main(void) {
    char buf[10];
    int n = snprintf(buf, sizeof(buf), "Hello, %s!", "World");
    printf("buf = \"%s\", required length = %d\n", buf, n);
    return 0;
}

buf = "Hello, Wo", required length = 13