how to read a text/binary file line by line in c-CodePudding

I am writing a program to make a copy of a file (binary or text) in c. The first thing i need to do is read the file, after doing some research i found the fgets() function.

However i found out that fgets() is deprecated and also according to a comment in that post fgets() will not stop when it encounters NUL:

null bytes do not belong in text files.
fgets() was designed to work with text files:
using fgets() with files of binary data is not recommended

fgets() seems incomplete for reading binary/text files line by line unless certain hacky and inelegant lines are added when reading.

So my question is, how can i safely and reliably read a binary/text file line by line?

CodePudding user response：

I am writing a program to make a copy of a file (binary or text) in c.

Use fwrite and fread.

Simple copy function (you need to open files before calling it)

#define READBUFFSIZE (64*1024)

int copyFile(FILE *source, FILE *dest)
{
    void *buff = malloc(READBUFFSIZE);
    long length;
    int result = 0;
 
    if(!source || !dest || !buff || fseek(source, 0, SEEK_END)) {result = -1; goto cleanup_exit;}
    length = ftell(source); 
    if(fseek(source, 0, SEEK_SET)) {result = -1; goto cleanup_exit;}
    while(length)
    {
        long chunk = length >= READBUFFSIZE ? READBUFFSIZE : length;
        if(fread(buff, 1, chunk, source) == -1) {result = -1; goto cleanup_exit;}
        if(fwrite(buff, 1, chunk, dest) == chunk) {result = -1; goto cleanup_exit;}
        length -= chunk;
    }
    cleanup_exit:
    free(buff);
    return result;
}

So my question is, how can i safely and reliably read a binary/text file line by line?

Binary files do not have lines - so you cant read them line by line.

Text files - use fgets

#define MAXLLINE    256

int main(int argc, char **argv)
{
    char buff[MAXLINE]
    if(argc >= 2)
    {
        FILE *fi = fopen(argv[1], "r");
        if(fi)
        {
            size_t line = 0;
            while(fgets(buff, MAXLINE, fi))
            {
                printf("[%zu] %s",   line, buff);
            }
        }
        else
        {
            /* error handling */
        }
    }
}

CodePudding user response：

Try creating a file pointer which is placed at the starting of the file and the file pointer is incremented so it can read each character and print it on console using a while loop until fileptr gets EOF.

It can implemented as:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
    FILE* ptr;
    char ch;
    ptr = fopen("test.txt", "r");
    if (NULL == ptr) {
        printf("file can't be opened \n");
    }
    printf("content of this file are \n");
    do {
        ch = fgetc(ptr);
        printf("%c", ch); 
    } while (ch != EOF);
    fclose(ptr);
    return 0;
}