CODEWITHSUNDEEP
bashif-statementsyntax
RootOfMinusOne
RootOfMinusOne

Reputation: 137

what is the difference between hitting `enter` after `then` and `;` in if condition

if i write this in a script it runs

if [[ 1 == 1 ]]
 then
   echo "true"
 fi

but if I tried to replace newline with ; when using an active shell i get syntax error

if [[ 1 == 1 ]]; then; echo "true"; fi

why?

what is the difference between hitting enter after then and ;

Upvotes: 1

Views: 46

Answers (1)

melpomene
melpomene

Reputation: 85767

The bash manual says:

In most cases a list of commands in a compound command’s description may be separated from the rest of the command by one or more newlines, and may be followed by a newline in place of a semicolon.

As well as:

The syntax of the if command is:

if test-commands; then
  consequent-commands;
[elif more-test-commands; then
  more-consequents;]
[else alternate-consequents;]
fi

(I believe the formatting in the above description (multiple lines, indentation) is for the benefit of the human reader, not part of the formal syntax. That is, if test-commands; then consequent-commands; [elif more-test-commands; then more-consequents;] [else alternate-consequents;] fi would have the same meaning.)

The initial statement says ; in this description can be replaced by a newline, but not vice versa.

Instead it says you can optionally put newlines before and after the command lists, which are simply ignored.

Taking your example:

if [[ 1 == 1 ]]
 then
   echo "true"
 fi

Here we have test-commands of [[ 1 == 1 ]]. The syntax requires a ;, but because of the "may be followed by a newline in place of a semicolon" rule, we're fine (there is a following newline).

For the then consequent-commands; part, we have

 then
   echo "true"

This is fine because the consequent-commands (i.e. echo "true") "may be separated from the rest of the command [i.e. then in this case] by one or more newlines".

Again, the syntax requires a ; next, but instead we use a newline, as permitted by the initial rule.

Then we reach the fi and we're done.

Upvotes: 1

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