I have a string that contains a use of some variable, and I'd like to substitute that variable's value into the string. Right now the best I have is
#!/bin/bash
foo='$name; echo bar'
name="The name"
expanded="$(eval echo "$foo")"
echo "$expanded"
Which has some obvious defects: it prints
The name
bar
while I'd like it to print
The name; echo bar
Instead of eval you can do bash's regex matching with bash's string replacement:
foo='$name; echo bar'
name="The name"
[[ "$foo" =~ \$([[:alnum:]]+) ]] && s="${!BASH_REMATCH[1]}" &&
expanded="${foo/\$${BASH_REMATCH[1]}/$s}"
echo "$expanded"
The name; echo bar
${name:-default} etc
while loop.Not exactly sure what you are trying to do but this works and you do not have (nor probably want) to use eval:
name="The name"
foo="$name; echo bar"
echo "$foo
prints
The name; echo bar
foo is a command line parameter, so I have no chance to define it after name.You can do it like this:
#!/bin/bash
name="The ' \" name"
foo="$name; echo bar"
expanded=$(eval 'echo "$foo"')
echo "$expanded"
Output:
The ' " name; echo bar
The name; echo bar though (4 spaces). EDIT: spaces got collapsed by the comment system, they go between The and name.name contains ' though.