问题
I'm getting this error
Syntax error: redirection unexpected
in the line:
if grep -q "^127.0.0." <<< "$RESULT"
How I can run this in Ubuntu?
回答1:
if grep -q "^127.0.0." <<< "$RESULT"
then
echo IF-THEN
fi
is a Bash-specific thing. If you are using a different bourne-compatable shell, try:
if echo "$RESULT" | grep -q "^127.0.0."
then
echo IF-THEN
fi
回答2:
<<< is a bash-specific redirection operator (so it's not specific to Ubuntu). The documentation refers to it as a "Here String", a variant of the "Here Document".
3.6.7 Here Strings
A variant of here documents, the format is:
<<< word
The word is expanded and supplied to the command on its standard input.
A simple example:
$ cat <<< hello
hello
If you're getting an error, it's likely that you're executing the command using a shell other than bash. If you have #!/bin/sh at the top of your script, try changing it to #!/bin/bash.
If you try to use it with /bin/sh, it probably assumes the << refers to a "here document", and then sees an unexpected < after that, resulting in the "Syntax error: redirection unexpected" message that you're seeing.
zsh and ksh also support this syntax.
回答3:
It works for me on Ubuntu, if I complete you IF block:
if grep -q "^127.0.0." <<< "$RESULT"; then echo ""; fi
来源：https://stackoverflow.com/questions/58478964/what-do-three-left-angle-brackets-mean-in-bash