Command to print to file linux

Redirect all output to file in Bash [duplicate]

I know that in Linux, to redirect output from the screen to a file, I can either use the > or tee . However, I’m not sure why part of the output is still output to the screen and not written to the file. Is there a way to redirect all output to file?

9 Answers 9

That part is written to stderr, use 2> to redirect it. For example:

foo > stdout.txt 2> stderr.txt 

or if you want in same file:

Note: this works in (ba)sh, check your shell for proper syntax

well, i found the reference and have deleted my post for having incorrect information. from the bash manual: ‘»ls 2>&1 > dirlist» directs only the standard output to dirlist, because the standard error was duplicated from the standard output before the standard output was redirected to dirlist» 🙂

also from the bash man «There are two formats for redirecting standard output and standard error: &>word and >&word Of the two forms, the first is preferred. This is semantically equivalent to >word 2>&1»

Two important addenda: If you want to pipe both stdout and stderr, you have to write the redirections in the opposite order from what works for files, cmd1 2>&1 | cmd2 ; putting the 2>&1 after the | will redirect stderr for cmd2 instead. If both stdout and stderr are redirected, a program can still access the terminal (if any) by opening /dev/tty ; this is normally done only for password prompts (e.g. by ssh ). If you need to redirect that too, the shell cannot help you, but expect can.

All POSIX operating systems have 3 streams: stdin, stdout, and stderr. stdin is the input, which can accept the stdout or stderr. stdout is the primary output, which is redirected with > , >> , or | . stderr is the error output, which is handled separately so that any exceptions do not get passed to a command or written to a file that it might break; normally, this is sent to a log of some kind, or dumped directly, even when the stdout is redirected. To redirect both to the same place, use:

EDIT: thanks to Zack for pointing out that the above solution is not portable—use instead:

If you want to silence the error, do:

Источник

Redirect Linux Command Output to File

Want to analyze the effect of Linux command for later? Here’s how you can save Linux command output to a file.

There are times when you want to redirect the output of specific output to a file so you can examine the error later.

And in that case, you can redirect the data stream to the file.

So in this tutorial, I will walk you through how to redirect the output to a file.

How to redirect output to file

Before I jump to the how-to part, it is necessary to know the basics of data streams.

There are 3 three types of data streams:

• Input data stream (denoted as 0)
• Output data stream (denoted as 1)
• Error data stream (denoted as 2)

You can not use 0 to redirect the input data stream. For that, you have to use < or you can pipe command.

Now, let’s have a look at redirection symbols and numbers for redirection:

Indicator	Description
0	Input data stream.
1	Output data stream.
2	Error data stream.
>	Redirects std output to a file or command.
	Redirects std input from a file or command.
>>	Appends the std output to a file.
2>	Redirects std error to a file or command.
2>>	Appends std error to a file.

Let’s have a look at examples.

1. Redirecing output to a file (overrides existing data)

As I mentioned above, you have to use the > symbol in the following manner:

For example, here, I used the sudo apt update command and redirected the output to the update.txt file:

sudo apt update > update.txt

And now, if I use the cat command to print the content of the file, it should bring the output of the apt update command:

But wait, if you use to redirect the output in the shown way, it will override the existing content of the file.

2. Redirect output to a file without overriding

As I mentioned earlier, if you don’t want to override the existing file content, then you use the >> instead of > :

For example, here, I will be using a sample text file named Hello.txt which contains the following:

And now, I will use the print command and redirect the output to the Hello.txt file:

echo Lines to be appended >> Hello.txt

Bonus: Redirect output using the tee command

Unlike redirection, using the tee command you can only override the existing file content to redirect its data.

If you don’t like the idea of using the redirection indicators, you can use the tee command in the following manner to have the same effect:

Here I used the file named Hello.txt which already had some text inside:

echo Hello again | tee Hello.txt

More on redirection of data

If you want to learn more about how you redirect the data streams with multiple possibilities, here’s a detailed guide for you:

I hope you will find this guide helpful.

Источник

How do I save terminal output to a file?

How do I save the output of a command to a file? Is there a way without using any software? I would like to know how.

10 Answers 10

Yes it is possible, just redirect the output (AKA stdout ) to a file:

Or if you want to append data:

If you want stderr as well use this:

if you want to have both stderr and output displayed on the console and in a file use this:

SomeCommand 2>&1 | tee SomeFile.txt 

(If you want the output only, drop the 2 above)

Note that someCommand 2> someFile.txt and someCommand 2>> someFile.txt also redirects stterr to someFile.txt

I’m trying to do this with gcc command but it doesn’t work. It works with other commands, but not this one. It simply creates the output file with nothing inside it.

@Nik-Lz Often this is because the command is sending all its output on stderr. If gcc is generating error messages, this seems likely. See Slothworks comment for how to capture stderr instead of stdout.

NB: to get the output of the make command into a file it requires this syntax instead: make > someFile.txt 2>&1 (source: linuxquestions.org/questions/linux-newbie-8/…)

To write the output of a command to a file, there are basically 10 commonly used ways.

Overview:

_{Please note that the n.e. in the syntax column means «not existing».
There is a way, but it’s too complicated to fit into the column. You can find a helpful link in the List section about it.}

 || visible in terminal || visible in file || existing Syntax || StdOut | StdErr || StdOut | StdErr || file ==========++==========+==========++==========+==========++=========== > || no | yes || yes | no || overwrite >> || no | yes || yes | no || append || | || | || 2> || yes | no || no | yes || overwrite 2>> || yes | no || no | yes || append || | || | || &> || no | no || yes | yes || overwrite &>> || no | no || yes | yes || append || | || | || | tee || yes | yes || yes | no || overwrite | tee -a || yes | yes || yes | no || append || | || | || n.e. (*) || yes | yes || no | yes || overwrite n.e. (*) || yes | yes || no | yes || append || | || | || |& tee || yes | yes || yes | yes || overwrite |& tee -a || yes | yes || yes | yes || append 

List:

• command > output.txt The standard output stream will be redirected to the file only, it will not be visible in the terminal. If the file already exists, it gets overwritten.
• command >> output.txt The standard output stream will be redirected to the file only, it will not be visible in the terminal. If the file already exists, the new data will get appended to the end of the file.
• command 2> output.txt The standard error stream will be redirected to the file only, it will not be visible in the terminal. If the file already exists, it gets overwritten.
• command 2>> output.txt The standard error stream will be redirected to the file only, it will not be visible in the terminal. If the file already exists, the new data will get appended to the end of the file.
• command &> output.txt Both the standard output and standard error stream will be redirected to the file only, nothing will be visible in the terminal. If the file already exists, it gets overwritten.
• command &>> output.txt Both the standard output and standard error stream will be redirected to the file only, nothing will be visible in the terminal. If the file already exists, the new data will get appended to the end of the file..
• command | tee output.txt The standard output stream will be copied to the file, it will still be visible in the terminal. If the file already exists, it gets overwritten.
• command | tee -a output.txt The standard output stream will be copied to the file, it will still be visible in the terminal. If the file already exists, the new data will get appended to the end of the file.
• (*) Bash has no shorthand syntax that allows piping only StdErr to a second command, which would be needed here in combination with tee again to complete the table. If you really need something like that, please look at «How to pipe stderr, and not stdout?» on Stack Overflow for some ways how this can be done e.g. by swapping streams or using process substitution.
• command |& tee output.txt Both the standard output and standard error streams will be copied to the file while still being visible in the terminal. If the file already exists, it gets overwritten.
• command |& tee -a output.txt Both the standard output and standard error streams will be copied to the file while still being visible in the terminal. If the file already exists, the new data will get appended to the end of the file.

Источник

How to print Linux command output to a file?

I am creating a script to sync my important documents between two system. I want my script to generate a log file for the last action. can you suggest me a way to achieve this. Question: If I execute the rsync command with -v flag, it will print a lot of messages on the console. Is there any way. So, I can redirect these logs to a file?

Here is short introduction how you can redirect the different kinds of output: tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-3.html

4 Answers 4

You can call your script and redirect «standard output» (AKA STDOUT) to a log file. Use ‘>>’ to append to the log file or ‘>’ to overwrite the log file. The file will be created (if permissions on it’s directory allow) if it doesn’t already exist. If the file already exists, make sure it is writeable by you (or whoever runs your script).

If you always append to the log file rather than write over it, it is good practice to make sure from the very beginning that something will «rotate» your log file, that is, move it to some other name and remove older log files. If the log file is unique to your script, you could have your script take care of log file rotation.

Usually, the preferred way is to call your script with STDOUT redirected, but there may be times when you want to do the redirecting within the script itself for one or more commands. You can add «>> logfile» after any statement in a shell script to append STDOUT of that command to logfile. You can change that to «2>&1 >> logfile» to append both «standard error» (AKA STDERR) and STDOUT to logfile. You don’t usually want to have STDERR also go to the logfile as STDERR is usually used to notify whatever/whoever is running the script of a problem. But there are times and situations where you do want that. If you like, you can group commands in your script inside < and >and redirect STDOUT of the whole group at once by putting the redirection after that closing brace.

Источник