- Windows Command Append To File
- Append In Unix
- Append Content To A File In Unix
- Unix Append To File
- Linux Append File To File
Firstly, O_APPEND or the equivalent FILE_APPEND_DATA on Windows means that increments of the maximum file extent (file 'length') are atomic under concurrent writers. This is guaranteed by POSIX, and Linux, FreeBSD, OS X and Windows all implement it correctly. Linux / Unix: Use Cat Command To Append Data To a File. You can use the cat command to append data or text to a file. The cat command can also append binary data. The main purpose of the cat command is to display data on screen (stdout) or concatenate files under Linux or Unix like operating systems. To append a single line you can use the echo or printf command. Bash Append Text To a Variable last updated February 4, 2013 in Categories BASH Shell, CentOS. To read the content of differente files and append it to a variable. By the way “+=” did the trick. KSH redirect stdout and stderr to a file on Linux or Unix.
With the Bash shell in Linux it is quite simple to append the contents of one file to another, here we will cover how to perform file concatenation.
In this example we have two files, file1 and file2. Both files contain unique contents, and we want to join them both together without overwriting any of the data.
This can be done quite simply in bash and other shells by using ‘>>’ to append the contents with the ‘cat’ command, as shown below.
First we’ll create our example files. https://wnskiu.weebly.com/rent-download-3d-movies.html.
Now we will concatenate these files together, by adding file2 to the bottom of file1.
The first line above uses ‘>>’ to append the contents of file2 to the end of file1 without overwriting anything. The second line is simply used to output the contents of file1, showing that we have successfully appended the content of file2 to file1.
It’s important that ‘>>’ is used, as this appends the content. If instead ‘>’ was used, file1 would be deleted and replaced entirely with the contents of file2.
We can also add the contents of file1 and file2 into a completely new file, file3.
This way we don’t modify the original contents of either file1 or file2, and instead create a new file, file3, which contains the contents of both file1 and file2 joined together.
As file3 does not exist here, it is created. If the file specified does exist it will be created, however if the destination file does exist the contents are simply appended on to the end of that file.
Summary
As shown we can use the ‘cat’ command and the ‘>>’ operator to append one file to another without removing the original content.
Active1 month ago
I have two files:
Ciro Santilli 新疆改造中心996ICU六四事件file1
and file2
. How do I append the contents of file2
to file1
so that contents of file1
persist the process?168k3636 gold badges642642 silver badges518518 bronze badges
asirasir4,71088 gold badges2020 silver badges1818 bronze badges
10 Answers
DavidDavid155k2929 gold badges155155 silver badges222222 bronze badges
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
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:
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:
.. https://wnskiu.weebly.com/zelda-a-link-between-worlds-ost-download.html. 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.
JoshMc6,12111 gold badge88 silver badges2525 bronze badges
T.RobT.Rob29k99 gold badges5252 silver badges9999 bronze badges
Note: if you need to use sudo, do this:
sudo bash -c 'cat file2 >> file1'
The usual method of simply prepending
jdunkjdunksudo
to the command will fail, since the privilege escalation doesn't carry over into the output redirection.2,07922 gold badges1212 silver badges1414 bronze badges
eumiroeumiro141k2222 gold badges245245 silver badges237237 bronze badges
jmatraszekjmatraszek
Just for reference, using ddrescue provides an interruptible way of achieving the task if, for example, you have large files and the need to pause and then carry on at some later point:
The
logfile
is the important bit. You can interrupt the process with Ctrl-C
and resume it by specifying the exact same command again and ddrescue will read logfile
and resume from where it left off. The -o A
flag tells ddrescue to start from byte A in the output file (file1
). So wc --bytes file1 | awk '{ print $1 }'
just extracts the size of file1
in bytes (you can just paste in the output from ls
if you like).As pointed out by ngks in the comments, the downside is that ddrescue will probably not be installed by default, so you will have to install it manually. The other complication is that there are two versions of ddrescue which might be in your repositories: see this askubuntu question for more info. Ti 84 plus doom game. The version you want is the GNU ddrescue, and on Debian-based systems is the package named
gddrescue
:For other distros check your package management system for the GNU version of ddrescue.
Windows Command Append To File
ZorawarAppend In Unix
Zorawar4,15122 gold badges1313 silver badges3535 bronze badges
Another solution:
tee
has the benefit that you can append to as many files as you like, for example:will append the contents of
file1
to file2
, file3
and file4
.From the man page:
Stefan van den AkkerStefan van den Akker4,32666 gold badges3232 silver badges5151 bronze badges
![How To Append Content To A File In Unix How To Append Content To A File In Unix](/uploads/1/3/3/9/133900790/948319211.png)
cat
can be the easy solution but that become very slow when we concat large files, find -print
is to rescue you, though you have to use cat once.2,19133 gold badges1818 silver badges2828 bronze badges
You can also do this without
cat
, though honestly cat
is more readable:>> file1 < file2
The
>>
appends STDIN to file1
and the <
dumps file2
to STDIN.Append Content To A File In Unix
Alok SinghAlok Singh
Unix Append To File
I am not sure about this, but many people have told me here that using
cat
command to display contents of a single file is not a good practice and someone shared this link with me.Consider all this, the following way seems better.
MihirLinux Append File To File
Mihir1,58222 gold badges22 silver badges1616 bronze badges