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.
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:
How to redirect output to a file and stdout
In bash, calling foo would display any output from that command on the stdout. Calling foo > output would redirect any output from that command to the file specified (in this case ‘output’). Is there a way to redirect output to a file and have it display on stdout?
If someone just ended up here looking for capturing error output to file, take a look at — unix.stackexchange.com/questions/132511/…
A note on terminology: when you execute foo > output the data is written to stdout and stdout is the file named output . That is, writing to the file is writing to stdout. You are asking if it is possible to write both to stdout and to the terminal.
@WilliamPursell I’m not sure your clarification improves things 🙂 How about this: OP is asking if it’s possible to direct the called program’s stdout to both a file and the calling program’s stdout (the latter being the stdout that the called program would inherit if nothing special were done; i.e. the terminal, if the calling program is an interactive bash session). And maybe they also want to direct the called program’s stderr similarly («any output from that command» might be reasonably interpreted to mean including stderr).
If we have multiple commands that want to pipe outputs, use ( ) . For example (echo hello; echo world) | tee output.txt
11 Answers 11
The command you want is named tee :
For example, if you only care about stdout:
If you want to include stderr, do:
program [arguments. ] 2>&1 | tee outfile 2>&1 redirects channel 2 (stderr/standard error) into channel 1 (stdout/standard output), such that both is written as stdout. It is also directed to the given output file as of the tee command.
Furthermore, if you want to append to the log file, use tee -a as:
program [arguments. ] 2>&1 | tee -a outfile If OP wants «all output» to be redirected, you’ll also need to grab stderr: «ls -lR / 2>&1 | tee output.file»
@evanmcdonnal The answer is not wrong, it just may not be specific enough, or complete depending on your requirements. There certainly are conditions where you might not want stderr as part of the output being saved to a file. When I answered this 5 years ago I assumed that the OP only wanted stdout, since he mentioned stdout in the subject of the post.
Ah sorry, I might have been a little confused. When I tried it I just got no output, perhaps it was all going to stderr.
Use -a argument on tee to append content to output.file , instead of overwriting it: ls -lR / | tee -a output.file
If you’re using $? afterwards it will return the status code of tee , which is probably not what you want. Instead, you can use $ .
$ program [arguments. ] 2>&1 | tee outfile 2>&1 dumps the stderr and stdout streams. tee outfile takes the stream it gets and writes it to the screen and to the file «outfile».
This is probably what most people are looking for. The likely situation is some program or script is working hard for a long time and producing a lot of output. The user wants to check it periodically for progress, but also wants the output written to a file.
The problem (especially when mixing stdout and stderr streams) is that there is reliance on the streams being flushed by the program. If, for example, all the writes to stdout are not flushed, but all the writes to stderr are flushed, then they’ll end up out of chronological order in the output file and on the screen.
It’s also bad if the program only outputs 1 or 2 lines every few minutes to report progress. In such a case, if the output was not flushed by the program, the user wouldn’t even see any output on the screen for hours, because none of it would get pushed through the pipe for hours.
Update: The program unbuffer , part of the expect package, will solve the buffering problem. This will cause stdout and stderr to write to the screen and file immediately and keep them in sync when being combined and redirected to tee . E.g.:
$ unbuffer program [arguments. ] 2>&1 | tee outfile