How do I append text to a file?
What is the easiest way to append text to a file in Linux?
I had a look at this question, but the accepted answer uses an additional program ( sed ) I’m sure there should be an easier way with echo or similar.
4 Answers 4
Essentially, you can dump any text you want into the file. CTRL-D sends an end-of-file signal, which terminates input and returns you to the shell.
Using the >> operator will append data at the end of the file, while using the > will overwrite the contents of the file if already existing.
You could also use printf in the same way:
Note that it can be dangerous to use the above. For instance if you already have a file and you need to append data to the end of the file and you forget to add the last > all data in the file will be destroyed. You can change this behavior by setting the noclobber variable in your .bashrc :
Now when you try to do echo «hello» > file.txt you will get a warning saying cannot overwrite existing file .
To force writing to the file you must now use the special syntax:
You should also know that by default echo adds a trailing new-line character which can be suppressed by using the -n flag:
Linux append text to end of file
You need to use the >> to append text to end of file. It is also useful to redirect and append/add line to end of file on Linux or Unix-like system.
How to redirect the output of the command or data to end of file
The procedure is as follows
- Append text to end of file using echo command:
echo ‘text here’ >> filename - Append command output to end of file:
command-name >> filename
How to add lines to end of file in Linux
The >> is called as appending redirected output. Create the file if does not exists. For example, append some networking command to net.eth0.config.sh script:
echo ‘I=eth0’ >> net.eth0.config.sh
echo ‘ip link set $I up’ >> net.eth0.config.sh
echo ‘ip addr add 10.98.222.5/255.255.255.0 dev $I’ >> net.eth0.config.sh
echo ‘ip route add default via 10.98.222.1’ >> net.eth0.config.sh
You can also add data to other config files. Another option is to run command and append output to a file. Run data command at the terminal and append output to output.txt:
date >> output.txt
Execute ls command and append data to files.txt:
ls >> files.txt
To see files.txt use cat command:
cat files.txt
more files.txt
less files.txt
How to append standard output and standard error
The following sytax allows both the standard output (file descriptor 1) and the standard error output (file descriptor 2) to be appended to the file name. The format for appending standard output and standard error is:
echo ‘text’ &>>filename
command &>>filename
find . type d -name «*.projects» &>> list.txt
This is semantically equivalent to
echo ‘text’ >>fileNameHere 2>&1
command >>fileNameHere 2>&1
date >>data.txt 2>&1 
For more info read redirection topic.
Append text when using sudo
Try the tee command:
echo ‘text’ | sudo tee -a my_file.txt
echo ‘104.20.186.5 www.cyberciti.biz’ | sudo tee -a /etc/hosts
Of coruse we can use following syntax to append text to end of file in Linux
sudo sh -c ‘echo my_text >> file1’
sudo — bash -c ‘echo «some data» >> /my/path/to/filename.txt’
The -c option passed to the bash/sh to run command using sudo.
See “how to append text to a file when using sudo command on Linux or Unix” for more info.
Conclusion – Append text to end of file on Unix
To append a new line to a text on Unix or Linux, try:
echo «text here» >> filename command >> filename date >> filename
How to append output to the end of a text file
How do I append the output of a command to the end of a text file?
10 Answers 10
Use >> instead of > when directing output to a file:
If file_to_append_to does not exist, it will be created.
Example:
To append a file use >>
then the output should be
To overwrite a file use >
then the out put is
You can use the >> operator. This will append data from a command to the end of a text file.
To test this try running:
Do this a couple of times and then run:
You’ll see your text has been appended several times to the textfile.txt file.
Use command >> file_to_append_to to append to a file.
For example echo «Hello» >> testFile.txt
CAUTION: if you only use a single > you will overwrite the contents of the file. To ensure that doesn’t ever happen, you can add set -o noclobber to your .bashrc .
This ensures that if you accidentally type command > file_to_append_to to an existing file, it will alert you that the file exists already. Sample error message: file exists: testFile.txt
Thus, when you use > it will only allow you to create a new file, not overwrite an existing file.
How To Append To File in C, using Open in O_APPEND Mode on linux?
This is part of a homework assignment. Well, I couldn’t get things working in my homework, so I’ve pulled a snippet out and started toying with it to figure out what’s wrong.
On linux in C I’m trying to open/create a text file, write something to it, close it, open it in read/write and append mode, and then append anything to the end of it (in this example, the string «, dude»). Nothing is being appended, though, but the write method is also not throwing an error. I’m not sure what’s up.
I’ve tried to eliminate the possibility of it being strictly a permissions issue by messing with a few different combinations, changing the mode variable to S_IRWXU | S_IRWXG | S_IRWXO, passing the mode as a third argument in my second open statement, only opening the file in append mode in the second open statement, passing the append mode as a third argument in the second open statement, etc.
The best I can do is open it in RDWR without the APPEND mode, and then write directly over the existing text. but that’s not what I want. And note, I’m aware of things like lseek, but the purpose here is strictly to use the append mode to add text to the end of the file. I don’t want to lseek.
Any clues from looking at this? I’m sure there’s something obvious I just don’t understand.
Append Lines to a File in Linux
Last modified: July 24, 2020
1. Introduction
In this tutorial, we’re going to explore several ways to append one or more lines to a file in Linux using Bash commands.
First, we’ll examine the most common commands like echo, printf, and cat. Second, we’ll take a look at the tee command, a lesser-known but useful Bash utility.
2. The echo Command
The echo command is one of the most commonly and widely used built-in commands for Linux Bash. Usually, we can use it to display a string to standard output, which is the terminal by default:
Now, we’re going to change the default standard output and divert the input string to a file. This capability is provided by the redirection operator (>). If the file specified below already contains some data, the data will be lost:
In order to append a line to our file.txt and not overwrite its contents, we need to use another redirection operator (>>):
Note that the ‘>’ and ‘>>’ operators are not dependent on the echo command and they can redirect the output of any command:
Moreover, we can enable the interpretation of backslash escapes using the -e option. So, some special characters like the new line character ‘\n’ will be recognized and we can append multiple lines to a file:
3. The printf Command
The printf command is similar to the C function with the same name. It prints any arguments to standard output in the format:
Let’s build an example and append a new line to our file using the redirection operator:
Unlike the echo command, we can see that the printf‘s syntax is simpler when we need to append multiple lines. Here, we don’t have to specify special options in order to use the newline character:
4. The cat Command
The cat command concatenates files or standard input to standard output.
It uses a syntax similar to the echo command:
The difference is that, instead of a string as a parameter, cat accepts one or more files and copies its contents to the standard output, in the specified order.
Let’s suppose we already have some lines in file1.txt and we want to append them to result.txt
Next, we’re going to remove the input file from the command:
In this case, the cat command will read from the terminal and appends the data to the file.txt.
So, let’s then type something into the terminal including new lines and then press CTRL + D to exit:
This will add two lines to the end of file.txt.
5. The tee Command
Another interesting and useful Bash command is the tee command. It reads data from standard input and writes it to the standard output and to files:
In order to append the input to the file and not overwrite its contents, we need to apply the -a option:
Once we hit Enter, we’ll actually see our same line repeated back to us:
This is because, by default, the terminal acts as both standard input and standard output.
We can continue to input how many lines we want and hit the Enter key after each line. We’ll notice that each line will be duplicated in the terminal and also appended to our file.txt:
Now, let’s suppose we don’t want to append the input to the terminal, but only to a file. This is also possible with the tee command. Thus, we can remove the file parameter and redirect the standard input to our file.txt by using the redirection operator:
Finally, let’s take a look at the file.txt‘s contents:
6. Conclusion
In this tutorial, we’ve described a few ways that help us append one or more lines to a file in Linux.
First, we’ve studied the echo, printf and cat Bash commands and learned how we can combine them with the redirection operator in order to append some text to a file. We’ve also learned how to append the content of one or more files to another file.
Second, we’ve examined the lesser-known tee command that already has a built-in mechanism of appending some text to a file and doesn’t necessarily need the redirection operator.