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+====== Argc and Argv (Example 1) ======
+**Concepts:**\\
+Command line arguments.
+**Text:**\\
+Implement a C program that receives through the command line a string as input. The program must transform the content of the string in uppercase letters and print it on the screen.
+The option ''-c <number>'' between the name of the program and the string is used to convert and print only the first ''<number>'' characters of the string.
+Examples:
+<code bash>
+C:> prog_name.exe a_string_123
+A_STRING_123
+C:> prog_name.exe -c 4 a_string_123
+A_ST
+</code>
+**Soluzions:**\\
+Two solutions will be provided.
+**Solution 1:**\\
+In this first solution, less complex, no controls have been performed on command line parameters. The hypotesis is that the user of the program use it in a correct way.
+<file C argc_argv_1a.c>
+/*
+Implement a C program that receives through the command line a string as input.
+The program must transform the content of the string in uppercase letters and print it on the screen.
+The option '-c <number>' between the name of the program and the string is used to convert
+and print only the first <number> characters of the string.
+*/
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+#define LEN 50
+int main(int argc, char *argv[]) {
+    int i;
+    char s[LEN+1];
+    int string_length;
+    /* Running the program as follows:
+       prog_name.exe -c 4 sTriNg
+       the variables *argv[] and argc contains the following values:
+    argv[0]="prog_name.exe"
+    argv[1]="-c"
+    argv[2]="4"
+    argv[3]="sTriNg"
+    argc=4
+    And the output of the program will be STRI
+    */
+    if(argc==4){ /* If the user has specified the option -c */
+      string_length = atoi(argv[2]);
+      strncpy(s, argv[3], string_length);
+      s[string_length] = '\0';
+    }else{ /* If the only argument is <string> */
+      strcpy(s, argv[1]);
+      string_length = strlen(s);
+    }
+    for(i=0; i<string_length; i++){
+      s[i] = toupper(s[i]);
+    }
+    printf("The resulting string is: %s\n", s);
+    return 0;
+}
+</file>
+**Solution 2:**\\
+In this second solution, all the needed controls on command line arguments have been performed. Unfortunately, at the expense of the program readability.
+<file C argc_argv_1b.c>
+/*
+Implement a C program that receives through the command line a string as input.
+The program must transform the content of the string in uppercase letters and print it on the screen.
+The option '-c <number>' between the name of the program and the string is used to convert
+and print only the first <number> characters of the string.
+*/
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+#define LEN 50
+int main(int argc, char *argv[])
+{
+    int i;
+    char s[LEN+1];
+    int string_length;
+    /* Running the program as follows:
+       prog_name.exe -c 4 sTriNg
+       the variables *argv[] and argc contains the following values:
+    argv[0]="prog_name.exe"
+    argv[1]="-c"
+    argv[2]="4"
+    argv[3]="sTriNg"
+    argc=4
+    And the output of the program will be STRI
+    */
+    /* Check on the number of command line arguments */
+    if(argc!=2 && argc!=4) {
+        printf("Error: the program must be executed with the following arguments\n");
+        printf("%s (-c <number>)? <string>\n", argv[0]);
+        exit(-1) ; /* As the return 1; command, but with exit() the program is killed also
+                   if executed inside a function */
+    }
+    if(argc==4) { /* If the user has specified the option -c */
+      /* Control if argv[1] contains -c */
+      if(strcmp(argv[1], "-c")!=0){
+        printf("Error, the only available option is -c\n");
+        exit(-2);
+      }
+      /* Control if the second arguments is a number */
+      for(i=0; i<strlen(argv[2]); i++){
+        if(isdigit(argv[2][i])==0){
+          printf("Error: the argument of the -c option must be a number\n");
+          exit(-3);
+        }
+      }
+      string_length = atoi(argv[2]);
+      /* string_length = atoi(argv[2]); can be substituted with the command */
+      /* sscanf(argv[2], "%d", &string_length); */
+      printf("STRING LENGTH: %d\n", string_length);
+      /* Control if the number (i.e., the variable string_length) is positive */
+      if(string_length < 0){
+        printf("The number of the -c option must be positive or equal to 0\n");
+        exit(-4);
+      }
+      /* If the actual string is shorter then string_length, set the value
+         of string_length of the actual length of the string */
+      if (string_length > strlen(argv[3])) string_length = strlen(argv[3]);
+      /* Control if the string contained in argv[3] can be stored in s */
+      if(strlen(argv[3])>LEN){
+        printf("Error: <string> too long\n") ;
+        exit(-5);
+      }
+      /* The string has been stored inside the array s (a better solution can exploit directly argv[3]) */
+      strncpy(s, argv[3], string_length);
+      s[string_length] = '\0';
+    }else{ /* If the only argument is <string> */
+      /* Control if the string contained in argv[3] can be stored in s */
+      if(strlen(argv[1])>LEN){
+        printf("Error: <string> too long\n") ;
+        exit(-5) ;
+      }
+      /* Store the string */
+      strcpy(s, argv[1]);
+      string_length = strlen(s);
+    }
+    for(i=0; i<string_length; i++){
+      if(!isprint(s[i])){
+        printf("The string is not valid. Some characters are not printable\n");
+        exit(-6);
+      }
+      s[i] = toupper(s[i]);
+    }
+    printf("The resulting string is: %s\n", s);
+    return 0;
+}
+</file>

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