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Title:
echo "hello" >&0 | > file.txt doesn't write to file.txt
ID:
/2018/03/29/echo-_hello_-__0-_-_-file.txt-doesn_t-write-to-file.txt
Created:
March 29, 2018
Edited: March 29, 2018
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September 15, 2024
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- The
>symbol is for file redirection to start of a file. - The
>>symbol is for file redirection to the end of a file (append). - The
|symbol is for “piping” or passing the output from one command as input to another command.
$ echo "Hello" > file.txt
$ echo "World!" >> file.txt
$ cat file.txt
Hello
World!
$ cat file.txt | grep !
World!
The grep (Global regular expression print) command searches a file for a given search string and prints the line it is on.
The &>0 according to Advanced-Bash Scripting Guide:
&>filename
# Redirect both stdout and stderr to file "filename."
# This operator is now functional, as of Bash 4, final release.
In your case the file name was 0 which is standard input. So it is redirecting all output to input. Which as best as I can tell is a circular reference that will not work. The syntax you used is >&0 which redirects output to input. Which is also appears to be a circular reference.
The “filenames” are:
0standard input1standard output2standard error output
The traditional way of using file descriptor 0 (standard input) through file redirection is:
0< FILENAME
< FILENAME
# Accept input from a file.
# Companion command to ">", and often used in combination with it.
#
# grep search-word <filename
If you want to use the echo command and | together (as Zanna’s answer points out) you can use:
$ echo "hello" | cat > file.txt
$ cat file.txt
hello