bash - 如何声明本地整数？
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bash - How to declare a local integer?
提问by helpermethod
In Bash, how do I declare a local integer variable, i.e. something like:
在 Bash 中，我如何声明一个局部整数变量，例如：
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=0being used, but this doesn't look very portable.
我看到有人在某处local -i number=0使用，但这看起来不太便携。
回答by ecatmur
Per http://www.gnu.org/software/bash/manual/bashref.html#Bash-Builtins,
根据http://www.gnu.org/software/bash/manual/bashref.html#Bash-Builtins，
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.
local [option] name[=value] ...对于每个参数，都会创建一个名为 name 的局部变量，并为其分配值。该选项可以是declare 接受的任何选项。
So local -iis valid.
所以local -i是有效的。
回答by Paused until further notice.
declareinside a function automatically makes the variable local. So this works:
declare在函数内部自动使变量成为局部变量。所以这有效：
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:
输出是：
Before the function, $number has the value 10
In func, $number has the value 20
After the function, $number has the value 10
回答by not2qubit
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:
如果您最终使用的是 Android shell 脚本，您可能想知道 Android 使用的是 MKSH 而不是完整的 Bash，后者会产生一些影响。看一下这个：
#!/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:
运行这个，我们得到：
# 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 Androiddeclaredoesn't exist. But reading up, the others should be equivalent.
因此在Androiddeclare中不存在。但是读起来，其他的应该是等价的。
