- 結果をechoで表示して終わる、
- 結果をグローバル変数に書き込む、
そこで「 "From Bash to Z shell", O. Kiddle et.al., ISBN13:978-1-59059-379-9」を探ってみると、「Chapter 12, Variable Indirection, pp305..306」に「function double」の解説があったので試してみた；
#!/bin/zsh
double()
{
#local i=${!1} # Bash style didn’t work
local i=${(P)1} # Zsh style works well.
(( i=i*2 ))
eval "$1='$i'"
}
echo ---- test of double ---------------
num=$((3))
echo "\$num=$num before call of 'double'"
echo -----------------------------------
set -x
double num
set +x
echo -----------------------------------
echo "\$num=$num after call of 'double'"
echo -----------------------------------
その動作結果；
u1@MmM11[~/myZsh]% double
---- test of double ---------------
$num=3 before call of 'double'
-----------------------------------
+/Users/u1/myZsh/double:18> double num
+double:3> local 'i=3'
+double:4> (( i=i*2 ))
+double:5> eval 'num='\''6'\'
+(eval):1> num=6
+/Users/u1/myZsh/double:19> set +x
-----------------------------------
$num=6 after call of 'double'
-----------------------------------
u1@MmM11[~/myZsh]%
Googleで関連を調べると、少数ながら有用なサイトが見つかった；
- Bash and Zsh pointer
- http://yogsototh.wordpress.com/2008/07/03/bash-or-zsh-pointer/
- Double and triple substitution in bash and zsh
- http://unix.stackexchange.com/questions/68042/double-and-triple-substitution-in-bash-and-zsh
- answered Mar 24 '13 at 3:24 by Gilles
- How to return a string value from a bash function
- http://stackoverflow.com/questions/3236871/how-to-return-a-string-value-from-a-bash-function
- answered Jul 14 '10 at 2:39 by bstpierre
#!/bin/zsh
double_2() # General template for pointer like function.
{
local p=$1 # Set a pointer,p as the address,num in $1;
# like 「p=&num」 in C language.
local i=${(P)p} # Read the pointing value,*p & Set to a variable,i;
# like 「i=*p」 in C language.
#(( i=i*2 )) # It works well. But,
i=$((i*2)) # I prefer the left form rather than the above form.
eval "$p='$i'" # Write new value,i to the pointing value *p.
# like 「*p=i」 in C language.
# '$i': single quotes are necessary
# for the variable including spaces.
}
echo ---- test of double_2 -------------
num=$((4))
echo "\$num=$num before call of 'double_2'"
echo -----------------------------------
set -x
double_2 num
set +x
echo -----------------------------------
echo "\$num=$num after call of 'double_2'"
echo ------------------------------------
その動作結果；u1@MmM11[~/myZsh]% double_2 23:10:40
---- test of double_2 -------------
$num=4 before call of 'double_2'
-----------------------------------
+/Users/u1/myZsh/double_2:27> double_2 num
+double_2:2> local 'p=num'
+double_2:4> local 'i=4'
+double_2:7> i=8
+double_2:8> eval 'num='\''8'\'
+(eval):1> num=8
+/Users/u1/myZsh/double_2:28> set +x
-----------------------------------
$num=8 after call of 'double_2'
------------------------------------
u1@MmM11[~/myZsh]% 23:10:34
今回の環境をTerminalで確認した；
u1@MmM11[~]% zsh --version 11:03:16
zsh 5.0.2 (x86_64-apple-darwin13.0)
u1@MmM11[~]% sw_vers 11:03:20
ProductName:Mac OS X
ProductVersion:10.9.5
BuildVersion:13F34
u1@MmM11[~]% 11:03:25
このページの履歴
- 開始 2014-12-28(日) 23:18:01
- 追加 2014-12-29(月) 13:51:58 「Terminalで確認 」を直接htmlで放り込んだ。スペースの調節が難しい。
