Question

How to convert uppercase characters to lowercase and vice versa in text file with C

Answer 1

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
     
void deleteLine(char file[], const int lineNo, char newline[]) {
    char filetmp[100] = "tmp.txt";
    FILE *fp = fopen(file, "r");  
    FILE *fptmp = fopen(filetmp, "w");  
    
    if (fp == NULL || fptmp == NULL) {
        printf("Error open file\n");
        exit(EXIT_FAILURE);
    }
      
	char ch;
    while ( (ch = fgetc(fp)) != EOF) {
        if (isupper(ch))
            ch = tolower(ch);
        else if (islower(ch))
            ch = toupper(ch);
        fputc(ch, fptmp);
    }
      
    fclose(fp);
    fclose(fptmp);
      
    remove(file);
    rename(filetmp, file);
}
    
void readFile(char file[]) {
    FILE *fp = fopen(file, "r");
            
    char ch;
    while ((ch = fgetc(fp)) != EOF)
        putchar(ch);
     
    fclose(fp);
}
       
int main()
{
    char file[100] = "d:\\data.txt";
	char newline[100] = "nodejs Express";
        
    readFile(file);
        
    int lineNo = 2; 
    deleteLine(file, lineNo, newline);
    
    puts("\n");
    readFile(file);
    
    return 0;
}
        
          
          
          
/*
run:
          
C C++ c#
nodeJS Express
JavaScript PHP

c c++ C#
NODEjs eXPRESS
jAVAsCRIPT phpP
       
*/

 

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