C language-enter the file name in the command line and print the File Content

C language-enter the file name in the command line and print the File Content

In C language programming, argc and argv [] parameters in the main function are often encountered. Argc is the abbreviation of argument count, that is, the number of parameters; argv is the abbreviation of argument vector, that is, the parameter list. Argv [0] is the name of the program, argv [1] is the first program parameter input in the command line, argv [argc] is NULL, as shown below:

 

#include "stdio.h"

int main (int argc, char * argv [])
{
     printf ("the argc value is% d \ n", argc);

     int i;
     for (i = 0; i <= argc; i ++) {
         printf ("the argv [% d] value is% s \ n", i, argv [i]);
     }

     return 0;
}

#Compile the above code into a test executable file, enter the following at the command line
/ *
./test arg_1 arg_2
* /

#The results are as follows:
/ *
the argc value is 3
the argv [0] value is ./test_c_0
the argv [1] value is arg_1
the argv [2] value is arg_2
the argv [3] value is (null)
* /

After figuring out the argc and argv [], we can use the two to send the file name parameters to be processed to the program through the command line. The Code is as follows.

 

 

#include "stdio.h"

int main (int argc, char *argv[])
{
    FILE *fp;
    int c;

    fp = fopen( argv[1], "r");

    while ( (c = fgetc(fp)) != EOF){
        printf ("%c", c);
    }

    fclose(fp);

    return 0;
}