Writing to a file in C segmentation Fault-CodePudding

I have a function that gets a string from the user and then does the following


void TraverseFile(char *inFile, char *outFile)
{
    FILE *pIn;
    FILE *pOut;
    pIn = fopen(inFile, "r");
    char c;
    if (pIn == NULL)
    {
        printf("File not found");
    }
    pOut = fopen(outFile, "w");
    if (pOut == NULL)
    {
        fclose(pIn);
        printf("The write file cannot be opened.\n");
        exit(1);
    }
    else{
        while(1) //while it is not the end of input file
        {
            c= putchar(tolower(fgetc(pIn)));
            if (feof(pIn)) break;
            fputc(c,pOut);
        }
        fclose(pOut);
    }
    fclose(pIn);
}

Two things are happening: the while loop is giving me a segmentation fault. I think after input is because fgetc() returns in an int and I want to convert to a char. And the creation of the second file has a weird dot next to the txt name (see picture).

CodePudding user response：

At least these problems

Missing .h

Add

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

Wrong type

fgetc() returns an int to handle the typical 257 different return values. @Avi Berger

// char c;
int c;

Using a char value that is negative and not EOF is undefined behavior with tolower(). By saving in int, c will have a value in the unsigned char range or EOF.

while(!feof(pIn)) wrong

Why is “while( !feof(file) )” always wrong?

while((c = fgetc(pIn)) != EOF) {
  c = tolower(c);
  fputc(c,pOut);
}

Error lacks exit

When pIn == NULL, no point in continuing. @Retired Ninja

if (pIn == NULL) {
  printf("File not found");
  exit(1); // Add
}

Without an early exit, fclose(pIn); is undefined behavior as pIn==NULL.

Bad file name

OP has "creation of the second file has a weird dot next to the txt name". Certainly due to improper filename formation like insufficient buffer size for the name.