How to Save and Print an Input from stdin in Different Programming Languages

Collecting user input and storing it in a variable for further processing is a common task in programming. Different programming languages offer various methods to achieve this. In this article, we will explore how to save and print an input from stdin in Python and C.

Saving and Printing an Input in Python

In Python, you can save an input from stdin into a variable using the input function. This function prompts the user to input a line and stores it in the variable. Here’s a simple example:

Save the user’s input from stdin to a variable named user_input. Print the value of the variable.

Example in Python

user_input  input()  # Prompts the user to enter a line of (user_input)  # Prints the value stored in 'user_input'

When you run this code in a Python environment, it will wait for user input before printing the result.

For a more detailed explanation:

The input function takes an optional parameter, which is a prompt string to be displayed to the user. The value entered by the user is stored in the variable user_input. The print function is used to output the value of user_input.

Saving an Input in C Using the getline Function

In C, the getline function is a powerful way to read a whole line from stdin, including spaces. Here’s how you can do it:

Example in C

int main(){    char name[100];    printf("Enter your name: ");    getline(name, 100, stdin);    printf("You entered: %s
", name);    return 0;}

The getline function is defined in the stdio.h library and its syntax is:

ssize_t getline(char **lineptr, size_t *n, FILE *stream);

Here, name is the character array, and 100 is the size of the buffer. The getline function reads the entire line into the name array.

Note: The scanf and gets functions are deprecated and can be dangerous as they do not handle null character termination. The getline function is preferred for its safety and reliability.

Saving an Input in C Using gets and readline Functions

Another way to read a line of input in C is by using the gets function, although it is deprecated. Here’s an example:

Using the gets Function

#include stdio.hint main(){    char name[100];    printf("Enter your name: ");    gets(name);    printf("You entered: %s
", name);    return 0;}

This function reads a line of input into the name array and prints it.

If you’re concerned about the safety of the gets function, you can use a custom implementation like the readline function:

Using the readline Function

#include stdio.hvoid readline(char *s, int len){    char c;    char *p  s;    while(len  0)    {        c  getchar();        if (c  '
') c  0;        *p  c;        p  p   (c ! 0);        if (c  0) len  -1;        len--;    }}int main(){    char name[100];    printf("Enter your name: ");    readline(name, 99);    printf("You entered: %s
", name);    return 0;}

This function reads input character-by-character up to the newline character, which is treated as a null character terminator.

While getline is the recommended function, the readline function provides a safer alternative for environments where gets cannot be used.