Bash script that creates a bash script with variables

Question

I'm writing a Bash called "NewProject" that creates a second Bash script called "compile". Both scripts must be able to take arguments as input. My problem is that I can not write "$1" into the compile script - this simply copies the contents of NewProject's first argument into the compile script. This is the part of the NewProject script that creates the compile script.

echo "#!/bin/bash" > $1/compile
echo "
if [[ -z '$1' ]];
then
        echo "You are missing file names. Type in: compile -o executable files."
        exit 1
fi" >> $1/compile
chmod u+x $1/compile

And here is output from a test run of the NewProject script.

#!/bin/bash

if [[ -z 'testproject4' ]];

then
        echo You are missing file names. Type in: compile -o executable files.
        exit 1
fi

How can I change the NewProject script so that instead of 'testproject4', the compile script contains '$1'?

$ in "" gets interpreted, in '' it doesn't. Also note that you have internal " within your surrounding " (the "You are missing file names..." bit) which might not be what you intended (it doesn't matter in this case because echo echoes all its arguments separated by strings anyway) — mathematical.coffee
– mathematical.coffee, Commented Feb 5, 2014 at 23:26

Sasha · Accepted Answer · 2014-02-05 23:25:00Z

3

You should be more accurate with quoting.

echo "$1" >>$1/compile

will append the value of NewProject's first argument into the compile script.

However:

echo '$1' >>$1/compile

will append exactly $1 characters into the compile script.

answered Feb 5, 2014 at 23:25

Sasha

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2 Comments

Sasha Over a year ago

BTW:

echo "if [[ -z '$1' ]]; then echo "You are missing file names. Type in: compile -o executable files." exit 1 fi" >> $1/compile

will not work as you expect. Double quotes cannot be nested, so echo "aa "bb cc dd" ee" >>$1/compile will append aa bb cc dd ee (not aa "bb cc dd" ee) into compile. You should either escape inner "-s (echo "aa \"bb cc dd\" ee" >>$1/compile), or surround "-s with '-s.

Sasha Over a year ago

To insert $1 into compile, you can either use single quotes (echo '$1' >...) or escape $ with backslash (echo "\$1" >>...).

glenn jackman · Accepted Answer · 2014-02-05 23:34:35Z

0

I would use a heredoc

cat <<'END' > "$1"/compile
#!/bin/bash

if [[ -z $1 ]];
then
        echo "You are missing file names. Type in: compile -o executable files."
        exit 1
fi
END
chmod u+x "$1"/compile

When you quote the heredoc terminator word (cat <<'END'), it effectively quotes the entire doc

answered Feb 5, 2014 at 23:34

glenn jackman

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