英文:
How do I define and the call a function in Bash that loops through an array given as its parameter?
问题
以下是要翻译的内容：
在尝试定义一个循环遍历数组的函数时，注释显示了我遇到的错误：
#!/usr/bin/bash
local to_be_bckd_p=("lightningd.sqlite3" "emergency.recover")
prefs=("aaa" "bbbb")
echo_array() {
#for fl in "${1[@]}"; do echo "${fl}";done #${1[@]}: bad substitution
#for fl in "${*[@]}"; do echo "${fl}";done #${@[@]}: bad substitution
#for fl in "${@[@]}"; do echo "${fl}";done #${@[@]}: bad substitution
for fl in "${to_be_bckd_p[@]}"; do echo "${fl}";done
}
echo_fn() {
echo "${1}"
}
echo_array "${to_be_bckd_p[@]}"
echo_array "${prefs[@]}" #This loops through "${to_be_bckd_p[@]}"
echo_fn "Hi"
在函数定义中使用关键字 local 并不起作用。为什么在定义一个接受数组作为参数的函数时，${1} 不能正常工作，而在定义简单函数（如 echo_fn）时 ${1} 却能正常工作呢？
英文:
Comments show what errors I get when trying to define a function that loops through an array,
#!/usr/bin/bash
local to_be_bckd_p=("lightningd.sqlite3" "emergency.recover")
prefs=("aaa" "bbbb")
echo_array() {
#for fl in "${1[@]}"; do echo "${fl}";done #${1[@]}: bad substitution
#for fl in "${*[@]}"; do echo "${fl}";done #${@[@]}: bad substitution
#for fl in "${@[@]}"; do echo "${fl}";done #${@[@]}: bad substitution
for fl in "${to_be_bckd_p[@]}"; do echo "${fl}";done
}
echo_fn() {
echo ""
}
echo_array "${to_be_bckd_p[@]}"
echo_array "${prefs[@]}" #This loops through `"${to_be_bckd_p[@]}"`
echo_fn "Hi"
Using the keyword local in the function definition does not help.
Why using ${1} doesn't work in defining a function that is meant to take an array as its argument whereas ${1} works fine in the definitions of simpler functions such as echo_fn?
答案1
得分: 2
看起来您想将值传递给函数，而不是数组。可以通过`$@`数组的元素访问这些值：
```bash
#!/bin/bash
echo_array() {
for fl in "$@"; do
echo "$fl"
done
}
echo_fn() {
echo "$1"
}
to_be_bckd_p=("lightningd.sqlite3" "emergency.recover")
prefs=("aaa" "bbbb")
echo_array "${to_be_bckd_p[@]}"
echo_array "${prefs[@]}"
echo_fn "Hi"
<details>
<summary>英文:</summary>
It seems you want to pass the values to the function, not the array. The values can be accessed as the elements of the `$@` array:
```bash
#!/bin/bash
echo_array() {
for fl in "$@" ; do
echo "$fl"
done
}
echo_fn() {
echo "$1"
}
to_be_bckd_p=("lightningd.sqlite3" "emergency.recover")
prefs=("aaa" "bbbb")
echo_array "${to_be_bckd_p[@]}"
echo_array "${prefs[@]}"
echo_fn "Hi"
答案2
得分: 2
以下是翻译好的内容：
假设使用 bash 4.2+，我们可以使用 nameref 来控制数组（例如，访问数组索引）：
echo_array() {
declare -n _arr="$1" # nameref
for ndx in "${!_arr[@]}" # 遍历数组的索引
do
echo "$ndx : ${_arr[$ndx]}" # 打印 'index : value'
done
}
**注意：** `for val in "${_arr[@]}"` 将遍历数组的 *值*
来试一试：
```bash
$ echo_array to_be_bckd_p # 传递数组的名称
0 : lightningd.sqlite3
1 : emergency.recover
$ echo_array prefs # 传递数组的名称
0 : aaa
1 : bbbb
$ declare -A assoc=( [a]=1 [b]=2 [c]=3 ) # 添加一个关联数组到混合中
$ echo_array assoc # 传递数组的名称
a : 1
b : 2
c : 3
英文:
Assuming bash 4.2+, we can use a nameref to provide control of the array (eg, accessing array indices):
echo_array() {
declare -n _arr="$1" # nameref
for ndx in "${!_arr[@]}" # loop through array's indices
do
echo "$ndx : ${_arr[$ndx]}" # print 'index : value'
done
}
NOTE: for val in "${_arr[@]}" will loop through the array's values
Take for a test drive:
$ echo_array to_be_bckd_p # pass the name of the array
0 : lightningd.sqlite3
1 : emergency.recover
$ echo_array prefs # pass the name of the array
0 : aaa
1 : bbbb
$ declare -A assoc=( [a]=1 [b]=2 [c]=3 ) # add an associative array to the mix
$ echo_array assoc # pass the name of the array
a : 1
b : 2
c : 3
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