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fopen() function in C language with Example

Here, we are going to learn about the fopen() function of library header stdio.h in C language with its syntax, example.
Submitted by Souvik Saha, on January 09, 2019

fopen() function in C

Prototype:

    FILE *fopen(const char* filename, const char* mode);

Parameters:

    const char* filename, const char* mode

Return type: FILE*

Use of function:

The fopen() function opens a stream which links with a file. The prototype of this function is: FILE *fopen(const char* filename, const char* mode);

Where,

• filename: Name of the file which you want to work.
• mode: The operation modes like read, write etc.

fopen() example in C

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

int main()
{
    //create two files pointer
    FILE *f1, *f2;
    char s[20];

    //open file for reading
    f1 = fopen("includehelp.txt", "w");
    printf("File is created for write operation\n");

    printf("Enter any string\n");
    scanf("%s", &s);
    //enter the string into the file
    fputs(s, f1);
    fclose(f1);

    //append file for further operation
    f2 = fopen("includehelp.txt", "a");
    printf("File is appended\n\n");
    fprintf(f2, "%s", "_tutorial");
    fclose(f2);

    //check the file's existence
    if ((f2 = fopen("includehelp.txt", "r")) == NULL) {
        printf("file cannot open\n");
        exit(1);
    }

    //read the content from the file
    fscanf(f2, "%s", s);
    printf("%s", s);
    fclose(f2);

    return 0;
}

Output

C stdio.h Library Functions Programs »

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