In Bash, how can I check if a string begins with some value?

Question

I would like to check if a string begins with "node" e.g. "node001". Something like

if [ $HOST == user* ]   then   echo yes fi 

How can I do it correctly?

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I further need to combine expressions to check if HOST is either "user1" or begins with "node"

if [ [[ $HOST == user1 ]] -o [[ $HOST == node* ]] ]; then echo yes fi  > > > -bash: [: too many arguments 

How can I do it correctly?

Answer 1

This snippet on the Advanced Bash Scripting Guide says:

# The == comparison operator behaves differently within a double-brackets # test than within single brackets.  [[ $a == z* ]]   # True if $a starts with a "z" (wildcard matching). [[ $a == "z*" ]] # True if $a is equal to z* (literal matching). 

So you had it nearly correct; you needed double brackets, not single brackets.

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With regards to your second question, you can write it this way:

HOST=user1 if  [[ $HOST == user1 ]] || [[ $HOST == node* ]] ; then     echo yes1 fi  HOST=node001 if [[ $HOST == user1 ]] || [[ $HOST == node* ]] ; then     echo yes2 fi 

Which will echo

yes1 yes2 

Bash's if syntax is hard to get used to (IMO).