Is there a way to print all string in capital letters without using strupr function as its not a standard library function?

Question

I want to print the data stored in a file which is randomly cased in all caps and strupr() seems to be something that's been listed by someone previously but its not a standard function and may not be cross platform. Is there something which is cross platform?

EDIT 1:

                                fgets(input1,254,title);
                                fgets(input2,254,author);
                                input1[strcspn(input1, "\n")] = '\0';
                                input2[strcspn(input2, "\n")] = '\0';
                                printf("<%s> <%s>\n",input1,input2 );

I want to print the string stored in input1 and input2 in uppercase. How to do that?

the latter one @RobertSsupportsMonicaCellio – Jun 16 '20 at 09:18 — , Jun 16 '20 at 09:18

score 1 · Answer 1 · answered Jun 15 '20 at 07:15

1

You can process character by character and use toupper(). Standard function C89 onwards.

answered Jun 15 '20 at 07:15

Sourav Ghosh

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RobertS supports Monica Cellio · Answer 2 · 2020-06-16T08:42:06.950

0

You can use a custom made function, f.e. upcase(). It reads every character in the file, checks whether it is lowercase or not (if it is, the character is adjusted to uppercase using the toupper() function), stores the whole file content into a buffer and then overwrites the file with the content in the buffer:

FILE* upcase (const char* path)
{
    int c, cnt = 0, i = 0, j = 1;
    int n = 500;
    FILE* fp = fopen(path, "r+");

    char* buffer = calloc(n, sizeof(char));

    if (!fp || !buffer)
    {
       return NULL;
    }

    while ((c = fgetc(fp)) != EOF)
    {  
       if ( i == n )
       {
           j++;
           realloc(buffer, sizeof(char) * (n * j));

           if (!buffer)
           {
               return NULL;
           }

           i = -1;
       }  

       c = toupper(c);
       buffer[i] = c;

       i++;
       cnt++;
    }

    for ( int i = 0; i < cnt; i++ )
    {
        if (fputc(c, fp) == EOF)
        {
            fclose(buffer);
            return NULL;
        }
    }

    return fp;    
}

edited Jun 16 '20 at 08:42

answered Jun 15 '20 at 07:59

RobertS supports Monica Cellio

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Hmmm, Fails after `2*n`. Suggest `n = something` in the `if ( i == n )` block. – chux - Reinstate Monica Jun 15 '20 at 16:07
@chux-ReinstateMonica The idea is that `i` is reset, and `n` is the fixed measurement after how many `char` elements the memory is to be reallocated. I didn't intended to assign a new value to `n`, only `i`. – RobertS supports Monica Cellio Jun 15 '20 at 16:23
OK I now see that now. I do see a larger issue. Code does not use the return value of `realloc()`. The return value is needed as `realloc(buffer, sizeof(char) * (n * j));` does not change `buffer`. – chux - Reinstate Monica Jun 15 '20 at 18:25
Code also never uses `buffer[]` after filling it nor does it free `buffer`. `fputc(c, fp)` repeatedly tries to print `EOF`. – chux - Reinstate Monica Jun 15 '20 at 18:29

score 0 · Accepted Answer · answered Jun 15 '20 at 11:15

Or you can check if character is in between a & z then do a - 32. It will be changed to capital letter.

Here a - 32 = A, because ASCII value of a is 97 and 97 - 32 = 65 and we all know that ASCII value of A is 65.

Code:

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

int main(void)
{
    FILE *fp;
    char buffer[255] = {'\0'}, c;
    int i = 0;

    fp = fopen("txt.txt", "r");

    if(!fp)
    {
        perror("txt");
        exit(1);
    }

    while( (c = getc(fp)) != EOF)
        buffer[i++] = c;

    for( i = 0; buffer[i] != '\0'; i++)
    {
        if(buffer[i] >= 'a' && buffer[i] <= 'z')
            buffer[i] = buffer[i] - 32;
        printf("%c", buffer[i]);
    }
    fclose(fp);
    return 0;
}

Output:

HELLO!
THIS IS 2ND LINE.

Is there a way to print all string in capital letters without using strupr function as its not a standard library function?

3 Answers3