open file in c code example

Example 1: read files in c

#include<stdio.h>
int main(){
	FILE *in=fopen("name_of_file.txt","r");
	char c;
	while((c=fgetc(in))!=EOF)
		putchar(c);
	fclose(in);
	return 0;
}

Example 2: write in file in c

#include<stdio.h>
int main(){
	FILE *out=fopen("name_of_file.txt","w");
	fputs("Hello File",out);
	fclose(out);
	return 0;
}

Example 3: int open file in c

#include <unistd.h>
#include <fcntl.h>
 
int main()
{
    int filedesc = open("testfile.txt", O_WRONLY | O_APPEND);
    if(filedesc < 0)
        return 1;
 
    if(write(filedesc,"This will be output to testfile.txt\n", 36) != 36)
    {
        write(2,"There was an error writing to testfile.txt\n");    // strictly not an error, it is allowable for fewer characters than requested to be written.
        return 1;
    }
 
    return 0;
}

Example 4: how to open a file with open in c

int main (void)
{
	int fd = open("path_name.c", O_RDONLY);  // the file is now open, you just need to read it
	return (0);
}

Example 5: write a binary file c

FILE *write_ptr;

write_ptr = fopen("test.bin","wb");  // w for write, b for binary

fwrite(buffer,sizeof(buffer),1,write_ptr); // write 10 bytes from our buffer

Example 6: file in C

//to open a file
FILE=*fp;
fp=fopen("one.txt", "w");
//to close file 
fclose(fp);