Output redirection

> >> 2>

Write a command's output to a file instead of the screen

How it works

A command normally prints its result on screen. > sends that output to a file instead: ls > files.txt. If the file does not exist it is created; if it does, its old contents are wiped.

>> appends the output to the end of the file and leaves what is there alone, which is how logs are kept. Errors go to a separate stream (stderr) and do not end up in the file with >; 2> is for them. To collect both output and errors in one file, write command > file 2>&1.

Careful. > wipes the file without warning. Mixing up > and >> is a common way to lose a log or a config.

Syntax

<command> > <file>
<command> >> <file>
<command> 2> <file>
<command> > <file> 2>&1

Examples

Write the file list to files.txt (overwriting it)
```
ls > files.txt
```
same as: ls >files.txt
- ls — list files
- > — output to a file, old contents are erased
- files.txt — file
Append the line done to the end of log.txt
```
echo "done" >> log.txt
```
same as: echo done >> log.txt, echo 'done' >> log.txt, echo "done" >>log.txt
- echo "done" — print text
- >> — append to the end of the file
- log.txt — file
Run npm test and save only the errors to errors.log
```
npm test 2> errors.log
```
same as: npm test 2>errors.log
- npm test — command
- 2> — redirect the error stream (stderr)
- errors.log — file

Related commands

| — The pipe. Pass the output of one command to the input of another
echo — Print text or the value of a variable
cat — Print a file to the terminal

Practise · All commands