The variable BUILDNUMBER is set to value 230. I expect 230_ to be printed for the command echo $BUILDNUMBER_ but the output is empty as shown below.
# echo $BUILDNUMBER_
# echo $BUILDNUMBER
230
The command echo $BUILDNUMBER_ is going to print the value of variable $BUILDNUMBER_ which is not set (underscore is a valid character for a variable name as explicitly noted by Jeff Schaller)
You just need to apply braces (curly brackets) around the variable name or use the most rigid printf tool:
echo "${BUILDNUMBER}_"
printf '%s_\n' "$BUILDNUMBER"
PS: Always quote your variables.
answered Apr 11 '17 at 9:49
-
The documentation and the standard use the term "null" for a variable set to an empty string (as opposed to an unset variable). I took the liberty of editing. – ilkkachu Apr 11 '17 at 10:04
As George Vassiliou already explained, that's because you're printing the variable $BUILDNUMBER_ instead of $BUILDNUMBER. The best way to get what you want is to use ${BUILDNUMBER}_ as George explained. Here are some more options:
$ echo "$BUILDNUMBER"_
230_
$ echo $BUILDNUMBER"_"
230_
$ printf '%s_\n' "$BUILDNUMBER"
230_
-
We know what the variable holds, but we don't know what
$IFSholds, soecho $BUILDNUMBER"_"is still wrong. Of the three, onlyprintf '%s_\n' "$BUILDNUMBER"is correct if we don't know what$BUILDNUMBERor$IFShold. – Stéphane Chazelas Jan 31 '19 at 8:05
