Unix Bourne Shell中的数组

我正在尝试在Bourne shell（/bin/sh）中使用数组。我发现初始化数组元素的方法是：

arr=(1 2 3)

但是它遇到了一个错误：

syntax error at line 8: `arr=' unexpected

现在我发现该语法的帖子说的是for bash，但是我找不到Bourne shell的任何单独语法。语法/bin/sh也一样吗？

/bin/sh如今在任何系统上几乎都不是Bourne外壳程序（即使Solaris是最后一个包含它的主要系统之一，现在也已在Solaris 11中将其/ bin / sh切换到POSIX sh）。/bin/sh是70年代初期的汤普森炮弹。1979年，Bourne shell在Unix V7中取代了它。

/bin/sh 此后多年一直是Bourne外壳程序（或Almquist外壳程序，BSD上的免费实现）。

如今，/bin/sh更常见的是POSIX sh语言的解释器或另一种解释器，它本身是基于ksh88语言的子集（以及一些不兼容的Bourne shell语言的超集）。

Bourne Shell或POSIX sh语言规范不支持数组。或者更确切地说，他们只有一个阵列：位置参数（$1，$2，$@，所以每个功能一个阵列以及）。

ksh88确实有您设置的数组set -A，但是在POSIX sh中没有指定该数组，因为语法很尴尬并且不太实用。

与阵列/列表变量其他外壳包括：csh/ tcsh，rc，es，bash（其中大部分是复制的ksh的语法ksh93的方式）， ，，yash 每一个不同的语法（Unix的的一次要被后继的壳，并且是最一致那些）...zshfishrcfishzsh

在标准中sh（也适用于Bourne shell的现代版本）：

set '1st element' 2 3 # setting the array

set -- "$@" more # adding elements to the end of the array

shift 2 # removing elements (here 2) from the beginning of the array

printf '<%s>\n' "$@" # passing all the elements of the $@ array 
                     # as arguments to a command

for i do # looping over the  elements of the $@ array ($1, $2...)
  printf 'Looping over "%s"\n' "$i"
done

printf '%s\n' "$1" # accessing individual element of the array.
                   # up to the 9th only with the Bourne shell though
                   # (only the Bourne shell), and note that you need
                   # the braces (as in "${10}") past the 9th in other
                   # shells.

printf '%s\n' "$# elements in the array"

printf '%s\n' "$*" # join the elements of the array with the 
                   # first character (byte in some implementations)
                   # of $IFS (not in the Bourne shell where it's on
                   # space instead regardless of the value of $IFS)

（请注意，在Bourne shell和ksh88中，$IFS必须包含空格"$@"才能正常工作（错误），在Bourne shell中，您无法访问上面的元素$9（${10}不会起作用，您仍然可以执行shift 1; echo "$9"或循环执行他们））。

普通的Bourne外壳中没有数组。您可以使用以下方式创建数组并遍历它：

#!/bin/sh
# ARRAY.sh: example usage of arrays in Bourne Shell

array_traverse()
{
    for i in $(seq 1 $2)
    do
    current_value=$1$i
    echo $(eval echo \$$current_value)
    done
    return 1
}

ARRAY_1=one
ARRAY_2=two
ARRAY_3=333
array_traverse ARRAY_ 3

无论采用哪种方式使用数组，sh您都将选择它总是很麻烦。除非您只限于一个非常有限的平台或想学习一些东西，否则请考虑使用其他语言，例如Python或，Perl如果可以的话。

正如其他人所说的那样，Bourne Shell没有真正的数组。

但是，根据需要执行的操作，定界字符串就足够了：

sentence="I don't need arrays because I can use delimited strings"
for word in $sentence
do
  printf '%s\n' "$word"
done

如果典型的分隔符（空格，制表符和换行符）不够用，则可以IFS在循环之前设置为所需的任何分隔符。

而且，如果您需要以编程方式构建数组，则可以构建一个定界字符串。

一种模拟破折号的数组的方法（可以适应数组的任意数量的维）：（请注意，使用该seq命令要求将IFS其设置为''（SPACE =默认值）。您可以使用while ... do ...或do ... while ...循环而不是避免这种情况（我一直seq在更好地说明代码的作用）。

#!/bin/sh

## The following functions implement vectors (arrays) operations in dash:
## Definition of a vector <v>:
##      v_0 - variable that stores the number of elements of the vector
##      v_1..v_n, where n=v_0 - variables that store the values of the vector elements

VectorAddElementNext () {
# Vector Add Element Next
# Adds the string contained in variable $2 in the next element position (vector length + 1) in vector $1

    local elem_value
    local vector_length
    local elem_name

    eval elem_value=\"\$$2\"
    eval vector_length=\$$1\_0
    if [ -z "$vector_length" ]; then
        vector_length=$((0))
    fi

    vector_length=$(( vector_length + 1 ))
    elem_name=$1_$vector_length

    eval $elem_name=\"\$elem_value\"
    eval $1_0=$vector_length
}

VectorAddElementDVNext () {
# Vector Add Element Direct Value Next
# Adds the string $2 in the next element position (vector length + 1) in vector $1

    local elem_value
    local vector_length
    local elem_name

    eval elem_value="$2"
    eval vector_length=\$$1\_0
    if [ -z "$vector_length" ]; then
        vector_length=$((0))
    fi

    vector_length=$(( vector_length + 1 ))
    elem_name=$1_$vector_length

    eval $elem_name=\"\$elem_value\"
    eval $1_0=$vector_length
}

VectorAddElement () {
# Vector Add Element
# Adds the string contained in the variable $3 in the position contained in $2 (variable or direct value) in the vector $1

    local elem_value
    local elem_position
    local vector_length
    local elem_name

    eval elem_value=\"\$$3\"
    elem_position=$(($2))
    eval vector_length=\$$1\_0
    if [ -z "$vector_length" ]; then
        vector_length=$((0))
    fi

    if [ $elem_position -ge $vector_length ]; then
        vector_length=$elem_position
    fi

    elem_name=$1_$elem_position

    eval $elem_name=\"\$elem_value\"
    if [ ! $elem_position -eq 0 ]; then
        eval $1_0=$vector_length
    fi
}

VectorAddElementDV () {
# Vector Add Element
# Adds the string $3 in the position $2 (variable or direct value) in the vector $1

    local elem_value
    local elem_position
    local vector_length
    local elem_name

    eval elem_value="$3"
    elem_position=$(($2))
    eval vector_length=\$$1\_0
    if [ -z "$vector_length" ]; then
        vector_length=$((0))
    fi

    if [ $elem_position -ge $vector_length ]; then
        vector_length=$elem_position
    fi

    elem_name=$1_$elem_position

    eval $elem_name=\"\$elem_value\"
    if [ ! $elem_position -eq 0 ]; then
        eval $1_0=$vector_length
    fi
}

VectorPrint () {
# Vector Print
# Prints all the elements names and values of the vector $1 on sepparate lines

    local vector_length

    vector_length=$(($1_0))
    if [ "$vector_length" = "0" ]; then
        echo "Vector \"$1\" is empty!"
    else
        echo "Vector \"$1\":"
        for i in $(seq 1 $vector_length); do
            eval echo \"[$i]: \\\"\$$1\_$i\\\"\"
            ###OR: eval printf \'\%s\\\n\' \"[\$i]: \\\"\$$1\_$i\\\"\"
        done
    fi
}

VectorDestroy () {
# Vector Destroy
# Empties all the elements values of the vector $1

    local vector_length

    vector_length=$(($1_0))
    if [ ! "$vector_length" = "0" ]; then
        for i in $(seq 1 $vector_length); do
            unset $1_$i
        done
        unset $1_0
    fi
}

##################
### MAIN START ###
##################

## Setting vector 'params' with all the parameters received by the script:
for i in $(seq 1 $#); do
    eval param="\${$i}"
    VectorAddElementNext params param
done

# Printing the vector 'params':
VectorPrint params

read temp

## Setting vector 'params2' with the elements of the vector 'params' in reversed order:
if [ -n "$params_0" ]; then
    for i in $(seq 1 $params_0); do
        count=$((params_0-i+1))
        VectorAddElement params2 count params_$i
    done
fi

# Printing the vector 'params2':
VectorPrint params2

read temp

## Getting the values of 'params2'`s elements and printing them:
if [ -n "$params2_0" ]; then
    echo "Printing the elements of the vector 'params2':"
    for i in $(seq 1 $params2_0); do
        eval current_elem_value=\"\$params2\_$i\"
        echo "params2_$i=\"$current_elem_value\""
    done
else
    echo "Vector 'params2' is empty!"
fi

read temp

## Creating a two dimensional array ('a'):
for i in $(seq 1 10); do
    VectorAddElement a 0 i
    for j in $(seq 1 8); do
        value=$(( 8 * ( i - 1 ) + j ))
        VectorAddElementDV a_$i $j $value
    done
done

## Manually printing the two dimensional array ('a'):
echo "Printing the two-dimensional array 'a':"
if [ -n "$a_0" ]; then
    for i in $(seq 1 $a_0); do
        eval current_vector_lenght=\$a\_$i\_0
        if [ -n "$current_vector_lenght" ]; then
            for j in $(seq 1 $current_vector_lenght); do
                eval value=\"\$a\_$i\_$j\"
                printf "$value "
            done
        fi
        printf "\n"
    done
fi

################
### MAIN END ###
################