同时读取命令行 arguments 和字符串矩阵？ （在 C 中）

Question

So the following program doesn't know how many files will receive that's why I used a vector of pointers to store the pointers to all files. Anyway, the user must input from stdin a vector of strings and the reading stop when /exit is entered, but before that the command ./program file1 file2... fileN must be executed as well. After fileN the program takes the next following strings as command line arguments, which is not what I intended.

First:

./program file1.txt file2.jpg file3.in 

and stdin:

sort
alg
di
pi
food
/exit

Have a look:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, char *argv[])
{   char c;
    //Allocate memory for the file array based on the number of command line arguments
    FILE **f = malloc((argc-1)*sizeof(FILE*)); //invalid conversion from ‘void*’ to ‘FILE**’ {aka //‘_IO_FILE**’} [-fpermissive]
    int i;
    for (i=1; i<argc; i++) {
      printf("%s\n", argv[i]);
      f[i - 1] = fopen(argv[i],"r");
    }
    while((c= getchar()) != '\n' && c != EOF); //invalid conversion from ‘void*’ to ‘char**’  //[-fpermissive]
    char **text=malloc(300*sizeof(char*));
    for (i=0; i<=30; i++) //invalid conversion from ‘void*’ to ‘char**’ [-fpermissive]
      text[i]=malloc(300*sizeof(char));
   
    char s[30];
    int N=0;
    int ok=0;
    while (ok==0)
    {
       fgets(s,30,stdin);
       strcpy(text[N], s);
       if (strncmp(s,"/exit",5)==0)
         ok=1;
       N++;
    }
    for (i=0; i<N; i++)
    printf("%s\n", text[i]);

    // free memory after usage
    free(f);
    for(int i=0;i<30;i++) 
        free(text[i]);
    free(text);
    return 0;
}

When I press the run button it gives some weird errors like:

invalid conversion from ‘void*’ to ‘char**’ [-fpermissive]

or

invalid conversion from ‘void*’ to ‘FILE**’ {aka ‘_IO_FILE**’} [-fpermissive]

(see code). I changed the malloc to char text[300][300] but I still could not read the text from stdin. It should print the vector of strings but it doesn't do anything if I pass command line arguments and if I press run it just gives the errors above.

The program is meant to simply read file names as command line arguments (minimum number of arguments is 1 and maximum 9) and then a vector of strings from stdin and print the vector of strings in stdout.

(The files passed as command line arguments will be needed later to search matching strings with the strings from the vector of strings. I did not write code for that since the vector of strings is not read properly)

Can you help me read the command line arguments and the vector of strings at the same time?

Answer 1

The error message invalid conversion from 'void*' to 'char**' will appear if you are compiling the source code as c++ . Cast the result as text = (char **)malloc(.. ) to avoid it. If you are compiling the code as c , such error will not occur.

Based on your requirements, would you please try the following:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define EXIT_CODE "/exit"

int main(int argc, char *argv[])
{
    char **text = NULL;                 // array of strings
    char line[BUFSIZ];                  // line buffer while reading from stdin
    char *p;                            // temporal pointer on the input line
    int n = 0;                          // line counter of stdin
    int i;                              // general index
    FILE **fp;                          // array of file pointers

    if (NULL == (fp = malloc((argc - 1) * sizeof(FILE *)))) {
        perror("malloc");
        return EXIT_FAILURE;
    }
    for (i = 1; i < argc; i++) {        // open files in the arguments
        printf("%s\n", argv[i]);
        if (NULL == (fp[i - 1] = fopen(argv[i], "rb"))) {
            perror(argv[i]);
            return EXIT_FAILURE;
        }
    }

    while (fgets(line, BUFSIZ, stdin)) {
        if ((p = strrchr(line, '\n'))) *p = '\0';       // remove trailing newline, if any
        if ((p = strrchr(line, '\r'))) *p = '\0';       // remove trailing cr character, if any
        if (NULL == (text = realloc(text, (n + 1) * sizeof(char **)))) {
            perror("realloc");
            return EXIT_FAILURE;
        }
        if (NULL == (text[n] = malloc(strlen(line) + 1))) {
                                                        // allocate memory for the input line
            perror("malloc");
            return EXIT_FAILURE;
        }
        strcpy(text[n], line);
        n++;                                            // increment the line counter
        if (strncmp(line, EXIT_CODE, strlen(EXIT_CODE)) == 0) break;
    }

    // show the input from stdin
    for (i = 0; i < n; i++)
        printf("%s\n", text[i]);

    /*
     * do your processings of the input files here
     */

    // free memory after usage
    for (i = 1; i < argc; i++)
        fclose(fp[i - 1]);
    free(fp);
    for (i = 0; i < n; i++)
        free(text[i]);
    free(text);

    return EXIT_SUCCESS;
}