c fgets function

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Index

1. [[#fgets-function|fgets Function]]
2. [[#fgets-limitation-null-termination|fgets Limitation Null termination]]

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fgets Function

You can use fgets() function is used to read a line of text from a file or input from the user.

It is declared in the stdio.h header file as follows:

char *fgets(char *str, int n, FILE *stream);

The function takes three arguments:

• str: a pointer to the buffer where the line of text is stored
• n: the maximum number of characters to read
• stream: a pointer to the input stream to read from

The fgets function reads characters from the input stream until:

• it encounters a newline character ('\n')
• it encounters the end-of-file indicator (EOF)
• it has reached the maximum numbers of characters that can be stored in the variable (sizeof(fullName) - 1).
  • in the example above: (30 -1)

User Input Example:

char fullName[30];  
  
printf("Type your full name: \n");  
fgets(fullName, sizeof(fullName), stdin);  
  
printf("Hello %s", fullName);  
  
// Type your full name: John Doe  
// Hello John Doe

File Input Example:

#include <stdio.h>
 
int main() 
{
    char buffer[100];
    FILE *fp = fopen("example.txt", "r");
    if (fp == NULL) {
        printf("Failed to open file\n");
        return 1;
    }
    while (fgets(buffer, 100, fp) != NULL) {
        printf("%s", buffer);
    }
    fclose(fp);
    return 0;
}

This program opens a file named “example.txt” for reading, then reads lines from the file using fgets and prints them to the console using printf. Note that fgets reads at most 100-1 characters at a time to avoid buffer overflow.

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fgets Limitation: Null termination

fgets appends a null character ('\0') to the end of the string it reads, so:

• the buffer passed to fgets must be large enough to accommodate the null character.

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