In Bash, how do I declare a local integer variable, i.e. something like:
func() {
local ((number = 0)) # I know this does not work
local declare -i number=0 # this doesn't work either
# other statements, possibly modifying number
}
Somewhere I saw local -i number=0 being used, but this doesn't look very portable.
3 Answers
declare inside a function automatically makes the variable local. So this works:
func() {
declare -i number=0
number=20
echo "In ${FUNCNAME[0]}, \$number has the value $number"
}
number=10
echo "Before the function, \$number has the value $number"
func
echo "After the function, \$number has the value $number"
And the output is:
Before the function, $number has the value 10
In func, $number has the value 20
After the function, $number has the value 10
Per ,
local [option] name[=value] ...For each argument, a local variable named name is created, and assigned value. The option can be any of the options accepted by declare.
So local -i is valid.
In case you end up here with an Android shell script you may want to know that Android is using MKSH and not full Bash, which has some effects. Check this out:
#!/system/bin/sh
echo "KSH_VERSION: $KSH_VERSION"
local -i aa=1
typeset -i bb=1
declare -i cc=1
aa=aa+1;
bb=bb+1;
cc=cc+1;
echo "No fun:"
echo " local aa=$aa"
echo " typset bb=$bb"
echo " declare cc=$cc"
myfun() {
local -i aaf=1
typeset -i bbf=1
declare -i ccf=1
aaf=aaf+1;
bbf=bbf+1;
ccf=ccf+1;
echo "With fun:"
echo " local aaf=$aaf"
echo " typset bbf=$bbf"
echo " declare ccf=$ccf"
}
myfun;
Running this, we get:
# woot.sh
KSH_VERSION: @(#)MIRBSD KSH R50 2015/04/19
/system/xbin/woot.sh[6]: declare: not found
No fun:
local aa=2
typset bb=2
declare cc=cc+1
/system/xbin/woot.sh[31]: declare: not found
With fun:
local aaf=2
typset bbf=2
declare ccf=ccf+1
Thus in Android declare doesn't exist. But reading up, the others should be equivalent.
