What is the correct format for if then?
I tried lots of varieties.
Should the format work at the command line when not in a program?
$ if [1==2] then echo "y" fi;
> ;
-bash: syntax error near unexpected token `;'
4 Answers
Nobody explained the error yet.
You entered:
if [1==2] then echo "y" fi;
;
The first line was perfectly valid syntax as far as the shell was concerned. It is of the form:
if cmd args
In this case, cmd is derived from the expansion of the [1==2] glob. [1==2] is a globbing pattern that expands to the list of files in the current directory whose name consist of either a 1, = or 2 character.
For instance, if there's a file called 2 in the current directory, that becomes:
if 2 then echo fi;
That is run the 2 command with 4 arguments: 2, then, echo and fi, as the first command in the if part of an if/then/elif/else/fi statement.
The error comes from that second ; on the second line. You would have had the same error message by entering that ; alone on the command line. ; must be used to separate commands, it cannot be used on its own like that.
answered Sep 30, 2013 at 20:04
Stéphane Chazelas
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The correct form of the bash if construct is
if something; then command; fi
The correct form of what you seem to be attempting do do is
if [ 2 -eq 2 ]; then echo "y"; fi;
Spaces are important in bash.
Try this one:
if [ 1 == 2 ]; then echo "y" ; fi
And better use -eq, unless you want to compare 1 and 2 as a strings.
Useful link: http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_01.html
The == operator doesn't exist in Bash. It's either -eq when comparing numbers or = when comparing strings.
if [ 1 -eq 2 ]; then echo 'y'; fi
-
1
if,then,fi) should start their own separate lines. Or have semicolon in front of them:if [ 1 == 2 ]; then echo "y"; fi. Beside that, spaces around['s arguments are mandatory.[1==2]must have space between the[,]and the numbers, that is [ 1 -eq 2 ] as bash parser needs it.