Append from file linux

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

1. Append text to end of file using echo command:
   echo ‘text here’ >> filename
2. 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:

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How to Append to End of a File in Linux

In this tutorial, we learn different ways to append text to the end of a file in Linux. You can achieve this using several methods in Linux, but the simplest one is to redirect the command output to the desired filename. Using the >> character you can output result of any command to a text file.

Other ways this can be achieved, is using Linux tools like tee, awk, and sed.

Redirect output of command or data to end of file

Every Unix-based operating system has a concept of “a default place for output to go”. Everyone calls it “standard output”, or “stdout”, pronounced standard out. Your shell (probably bash or zsh) is constantly watching that default output place. When your shell sees new output there, it prints it out on the screen so that you can see it.

We can redirect that output to a file using the >> operator.

The procedure is as follows:

Append text to end of file using echo command:

Append command output to end of file:

Adding lines to end of file

We can add text lines using this redirect character >> or we can write data and command output to a text file. Using this method the file will be created if it doesn’t exist.

Adding command data output result to end of file

You can also add data or run command and append output to the desired file. In this example, we will use date for appending the current date to a file, uname command — which will print out kernel version of the Linux system we are using and lastly ls command which outputs the current directory structure and file list.
You can use any command that can output it’s result to a terminal, which means almost all of the command line tools in Linux.

Alternative methods

Let’s see how to append using tee, awk and sed Linux utility.

Using tee command line tool

Tee command reads the standard input and writes it to both the standard output and one or more files. The command is named after the T-splitter used in plumbing. It breaks the output of a program so that it can be both displayed and saved in a file.

Using awk command line tool

Awk is a utility that enables a programmer to write tiny but effective programs in the form of statements that define text patterns that are to be searched for in each line of a document and the action that is to be taken when a match is found within a line. Awk is mostly used for pattern scanning and processing.

Using sed command line tool

Sed command in Linux stands for stream editor and it can perform lots of functions on a file like searching, find and replace, insertion or deletion. By using sed you can edit files even without opening it, which is a much quicker way to find and replace something in the file.

Append multiple lines to a file

There are several ways to append multiple lines to a file at once.
You can, of course, add lines one by one:

Next variant is to enter new line in terminal:

Another way is to open a file and write lines until you type EOT:

Conclusion

Although there are multiple ways to append the text lines or data and command output to a file, we saw that the easiest way is using >> redirect character. There are ways to append the text to an end of a specific line number in a file, or in the middle of a line using regex, but we will going to cover that in some other article.

Let us know what method to append to the end of the file you think is best down in the comments section.

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how to append or add text to a file in linux

Append is defined as “to add something new to something that is existing, as an attachment or supplement“. Sometimes you will need to append text to an already existing text file. This text could come from any source, such as a line of text from the command line, the output of a command or from another text file.

The easiest way to append text is to use the operator ‘>>‘ from the Linux command line. There are two different operators that redirects output to files: ‘>‘ and ‘>>‘, that you need to be aware of.

‘>‘ is used to remove the previous contents before appending the text, while ‘>>‘ appends text while preserving the contents. And also, it always appends the text to the end of the file. So, if you want to append text then you should use the “>>” operator in your commands. We will see some examples of how this is done.

Append Single Line of Text

If you just want to quickly append a small single line of text, then you can use the echo command from the command line.

bash$ echo «This is just a single line of text» >> ./path/filename.txt

Append Text from Command Prompt (Multiple Lines)

If you want to append a long line of text or multiple lines then using the echo command can be cumbersome. In this case, you can direct the stand input (stdin) to the file instead.

When you use the following command, the cat command reads from the stdin and the “>>” operator redirects the standard input to the file, which means you will not return back to the prompt unless you exit (close the stream) using Ctrl-D

bash$ cat >> ./path/filename.txt

> to append text to file» width=558 height=151 data-ezsrcset=»/wp-content/uploads/linux-append-text-cat.png 558w, /wp-content/uploads/linux-append-text-cat-300×81.png 300w, /wp-content/uploads/linux-append-text-cat-258×70.png 258w» sizes=»(max-width: 558px) 100vw, 558px» data-ezsrc=/wp-content/uploads/linux-append-text-cat.png>

Note: use ctrl-d to exit the input mode

Append Text from another File

The text than you want to append can come from another text file. You can use the cat command along with the append operator to append the content.

bash$ cat myfile.txt >> ./path/filename.txt

You can also use the cat and append operators to merge multiple files as well. If you only want to append specific lines from the text file into the output file, then you may use the grep command to filter the output of cat and then append the results to file.

For example, the following command will append all lines that contain the word chocolate into the file chocolate.txt.

bash$ cat myfile.txt | grep -i «chocolate» >> ./path/chocolate.txt

Append Command Output to File

This works pretty much the same way as described with the earlier examples. The only requirement is that the command that you are using actually do output the results to the standard output.

bash$ date >> ./path/filename.txt

The above command appends the output of date command to the file name filename.txt. You can use any other command as well, such as time, ls, find or grep.

Using sed

Using the “>>” (append) operator is the easiest way to append text to a file from the command line. The other option that you have is the use of sed command.

The following example will append the line “Why redirection? I can use sed.” into the file filename.txt.

bash$ sed -i «$ a\Why redirection? I can use sed.» ./path/filename.txt

The one advantage of sed is that you actually use it to prepend text, as opposed the append. Prepend will add the new text to to the start of the file, while append adds it to the bottom or end of the file.

To prepend text to a file you can use the option 1i, as shown in the example below.

bash$ sed -i ‘1i This is the start of the file’ ./path/filename.txt

The sed command is a really powerful tool when it comes to the text manipulation. It is worthwhile reading through the documentation to find all its features.

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How to append multiple lines to a file

I am writing a bash script to look for a file if it doesn’t exist then create it and append this to it:

So «line then new line ‘tab’ then text» I think its a sensitive format. I know you can do this:

But it seems weird since its two lines. Is there a way to append that in this format:

10 Answers 10

If sudo (other user privileges) is needed to write to the file, use this:

Or, if it’s a literal tab that you want (rather than the four spaces in your question):

You can achieve the same effect with echo , but exactly how varies from implementation to implementation, whereas printf is constant.

Another approach is to use tee

A few choice lines from tee ‘s man page:

The tee utility copies standard input to standard output, making a copy in zero or more files.

-a — Append the output to the files rather than overwriting them.

Here is an example to append multiple lines in a file:

SED can append a line to the end of a file like so:

sed -i ‘$ a text to be inserted’ fileName.file
$ selects end of file, the a tells it to append, and after this comes the text that is to be inserted. Then of course the file name.

Does this approach have any added benefit than other solutions?
Yes, this approach has the added benefit of appending to any files return in a search, such as this: find . -name «*.html» -exec sed -i ‘$ a ‘ <> \;

I used the above example to insert the ending html tag that was missing on every html page within a number of directories.

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How to append one file to another in Linux from the shell?

I have two files: file1 and file2 . How do I append the contents of file2 to file1 so that contents of file1 persist the process?

8 Answers 8

cat file2 >> file1

The >> operator appends the output to the named file or creates the named file if it does not exist.

cat file1 file2 > file3

This concatenates two or more files to one. You can have as many source files as you need. For example,

cat *.txt >> newfile.txt

Update 20130902
In the comments eumiro suggests «don’t try cat file1 file2 > file1 .» The reason this might not result in the expected outcome is that the file receiving the redirect is prepared before the command to the left of the > is executed. In this case, first file1 is truncated to zero length and opened for output, then the cat command attempts to concatenate the now zero-length file plus the contents of file2 into file1 . The result is that the original contents of file1 are lost and in its place is a copy of file2 which probably isn’t what was expected.

Update 20160919
In the comments tpartee suggests linking to backing information/sources. For an authoritative reference, I direct the kind reader to the sh man page at linuxcommand.org which states:

Before a command is executed, its input and output may be redirected using a special notation interpreted by the shell.

While that does tell the reader what they need to know it is easy to miss if you aren’t looking for it and parsing the statement word by word. The most important word here being ‘before’. The redirection is completed (or fails) before the command is executed.

In the example case of cat file1 file2 > file1 the shell performs the redirection first so that the I/O handles are in place in the environment in which the command will be executed before it is executed.

A friendlier version in which the redirection precedence is covered at length can be found at Ian Allen’s web site in the form of Linux courseware. His I/O Redirection Notes page has much to say on the topic, including the observation that redirection works even without a command. Passing this to the shell:

. creates an empty file named out. The shell first sets up the I/O redirection, then looks for a command, finds none, and completes the operation.

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