This tutorial will show you a small example of C++ code on how to read a characters from a file, as well as to count the number lines that any particular file consist of. We will be creating the script and compiling the C++ on a Linux system. All distros will work the same, provided you have the G++ compiler installed, which we will cover as well.
In this tutorial you will learn:
- How to install G++ on major Linux distros
- C++ code for reading lines of a file
- Compiling and running C++ program to read characters of file

Category | Requirements, Conventions or Software Version Used |
---|---|
System | Any Linux distro |
Software | G++ or other C++ compiler |
Other | Privileged access to your Linux system as root or via the sudo command. |
Conventions |
# – requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command$ – requires given linux commands to be executed as a regular non-privileged user |
Install G++ on major Linux distros
In order to compile the C++ code that we present below, your system will have to have a C++ compiler installed. One of the best and most popular C++ compilers for Linux is G++. The GNU C++ Compiler is a compiler in Linux which was developed to compile C++ programs. The file extensions that can be compiled with G++ are .c and .cpp.
If you already have a different C++ compiler installed that you would prefer to use, that will work as well. Otherwise, use one of the following commands below to install the GNU C++ compiler with your Linux distribution’s package manager.
To install G++ on Ubuntu, Debian, and Linux Mint:
$ sudo apt install build-essential
To install G++ on CentOS, Fedora, AlmaLinux, and Red Hat:
$ sudo dnf install gcc-c++
To install G++ on Arch Linux and Manjaro:
$ sudo pacman -S gcc
Now that we have a compiler installed, move on to the section below to create the program.
C++ code to read characters from a file
Check out the C++ code below. The code will check for \n
, the “new line character” and increase the number of lines stored in the number_of_lines
integer variable. Every iteration will also print single character including \n
to an output.
- First, create a file called
my-input-file.txt
which will contain some text. For example:welcome to linuxconfig.org c++
- Then, copy c++ code below to a file called
read-characters.cpp
:#include
#include using namespace std; int main() { ifstream fin; fin.open("my-input-file.txt", ios::in); char my_character ; int number_of_lines = 0; while (!fin.eof() ) { fin.get(my_character); cout << my_character; if (my_character == '\n'){ ++number_of_lines; } } cout << "NUMBER OF LINES: " << number_of_lines << endl; }
- Next, compile the code with the following command.
$ g++ read-characters.cpp -o read-characters
- Execute the newly compiled binary file.
$ ./read-characters
NOTE: your text file must be located in the same directory as your executable read-characters program. The while loop and fin.get will add an extra new line character so you may want to use the following line to start counting at -1 instead:
int number_of_lines = -1

The output of the program in this example will be:
welcome to linuxconfig.org c++ NUMBER OF LINES: 4
Closing Thoughts
In this tutorial, we saw a C++ code snippet that can be used to count the number of lines in a text file. We also learned how to install the GNU C++ compiler on a variety of Linux distributions, so that our code can be compiled and run in a variety of environments.