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fgets() function in C

In C programming, handling input and output activities is essential. Fgets() is one of the many functions that are available for input. With the help of this robust function, developers may securely and precisely read information from a given stream. In this article, we will examine the ins and outs of fgets(), going over its syntax, application, sample code, and expected results.

The fgets() function, short for "file get string", is frequently used to read a string from a file stream or standard input (stdin). It provides a more secure substitute for the deprecated gets() function, which was previously used but now poses a security concern. The function fgets() offers a means to restrict the number of characters read and effectively handles newline characters.

Syntax for fgets() is as follows:

The parameters are broken out as follows:

str: It is a reference to the character array (string) that will be used to store the input.

size: The total number of characters (including the null character "0") that can be read.

stream: The pointing device to the input file stream or stdin that fgets() will read from.

In order to better grasp how fgets() functions, let's look at an example:



Enter a string: Hello, World!
You entered: Hello, World!
Enter a string: This is a very long string that exceeds the limit of the input buffer.
You entered: This is a very long string that exceeds the limit of the input buffer.
If a user types an empty text by simply pressing the Enter key:
Enter a string:
You entered:


In the above example, we begin by incorporating the appropriate header file, "stdio.h". After that, the input string is defined as a character array input with a size of 100.

Using printf() function, the program asks the user to enter a string. After that, stdin is used as the input stream, and fgets() is used with input as the destination string, sizeof(input), and maximum size to read. After that, the program uses printf() to output the entered string.

Fgets() function can read and save the newline character 'n' if it appears before the maximum size is reached. It makes it possible to tell if the input line was read entirely or truncated due to space constraints.


Using the modified code snippet, you can use the strcspn() method to delete the newline character from the input string:


Enter a string: Hello World
You entered: Hello World


The length of the substring made up of characters not in the supplied character set is determined by the strcspn() function. In this instance, the null character "0" is used to substitute the newline character after specifying "n" as the set of characters to search for.


In conclusion, reading input strings from file streams or standard input using the C fgets() method is dependable and secure. It is a useful tool for processing user input in a regulated manner because it allows you to select a maximum size for input and handles newline characters.

The deprecated gets() function is replaced by the more secure fgets() function, which fixes security flaws caused by buffer overflows. It makes sure that the input string does not become larger than what is allowed, avoiding potential memory corruption problems.

The provided example code shows how to use fgets() correctly to capture user input and remove the newline character if it appears. It emphasizes how crucial it is to take into account input constraints and deal with newline characters to ensure accurate string processing.

Developers can improve the security and robustness of their C programs with fgets(). They can avoid unexpected behaviors and potential security breaches brought on by large inputs by defining a maximum size for input.

Aspiring C programmers should become familiar with fgets() and its usage instructions to ensure secure and effective input handling. Developers that are aware of this function can produce more dependable and secure software that guards against input-related vulnerabilities that are frequently encountered.

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