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How can I echo the literal string -e and nothing else?
I'm trying to better understand how shell arguments are escaped.
The following commands do not work:
echo -e # prints nothing
echo '-e' # prints nothing
echo "-e" # prints nothing
echo \-e # prints nothing
echo \\-e # prints \-e
echo '\-e' # prints \-e
echo "'-e'" # prints '-e' (with quotes)
echo -- -e # prints -- -e
I can't find one that doesn't either include quotes or a leading slash.
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To print a string in Bash, use echo command. Provide the string as command line argument to echo command.
The -e option means "if any pipeline ever ends with a non-zero ('error') exit status, terminate the script immediately". Since grep returns an exit status of 1 when it doesn't find any match, it can cause -e to terminate the script even when there wasn't a real "error".
The echo command is used to display a line of text that is passed in as an argument. This is a bash command that is mostly used in shell scripts to output status to the screen or to a file.
The grep command can also be used to find strings in another string. In the following example, we are passing the string $STR as an input to grep and checking if the string $SUB is found within the input string. The command will return true or false as appropriate.
How to echo the literal string "-e" (and nothing else) in bash?
printf '%s\n' '-e'
printf -- '-e\n'
From man echo -e is an option:
-e
enable interpretation of backslash escapes
From bash builtins:
echo ...
If the -e option is given, interpretation of the following backslash-escaped characters is enabled.
...
echo does not interpret -- to mean the end of options.
So echo -e will make echo interpret -e as a flag and print empty newline.
To print -e you basically have to use printf (or you can use an implementation of echo that will allow to do that). I don't believe it is possible to print only -e with bash echo builtin.
printf is more portable. There are implementations of echo which do not take -e argument and it may work. On the net you can find various sites about echo portability issues.
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