Http://snailwarrior.blog.51cto.com/680306/154704BASH only supports one-dimensional arrays, but there is no limit to the number of parameters.
declares an array:
declare-a Array
(In fact, you don't have to declare it, you assign it directly to the variable as an array, and bash knows it's an array)
Array Assignment:
(1) array= (var1 var2 var3 ... varn)
(2) array= ([0]=VAR1 [1]=var2] [2]=var3 ... [N]=varn]
(3) array[0]=var1
Arrya[1]=var2
...
Array[n]=varn
To calculate the number of array elements:
${#array [@]}Or${#array [*]}Bash's special parameters @ and * Both denote "extended position parameters, starting from 1", but the form is slightly different, but it seems to be common in arrays.
Reference array:
echo ${array[n]}
To iterate over an array:
filename= (' ls ')
For Var in ${filename[@]};d o
Echo $var
Done
practical examples of arrays: (personal collection and collation)
1. Read n string from "standard input", and each input string is saved in arrayi=0
N=5
While ["$i"-lt $n]; Do
echo "Please input strings ... ' expr $i + 1 '"
Read array[$i]
b=${array[$i]}
echo "$b"
i= ' expr $i + 1 '
Done
2. Put the letters in the string into the array, and output to the "standard output"
chars= ' ABCDEFGHIJKLMNOPQRSTUVWXYZ '
for ((i=0; i<26; i++)); Do
array[$i]=${chars: $i: 1}
echo ${array[$i]}
DoneThe interesting place here is ${chars: $i: 1}, which means to get 1 characters starting from the $i position of the chars string. If you change 1 to 3, you get 3 characters ~ The result is: ABC
Bcd
...
Vxy
Xyz
YZ//There is not enough string to get the
z//Not enough string to get 3, apply array to Shell environment variable
3. Apply the array to the shell environment variable (1)Array Assignment:[[email protected] ~]# season= ("srping" "Summer" "Autumn" "Winter")When you find that the assignment is wrong, you can immediately correct it from the new assignment, as the above Spring is written as srping.
Re-assignment: (The original value is overridden)
[[email protected] ~]# season= ("Spring" "Summer" "Autumn" "Winter")Look at the environment variables:
[[email protected] ~]# Set | grep SEASON
season= ([0]= "Spring" [1]= "Summer" [2]= "Autumn" [3]= "Winter") displays the entire array:
[[email protected] ~]# echo ${season[*]}or Echo ${season[@]}
Spring Summer Autumn Winter displays an array element:
[[email protected] ~]# echo ${season[3]}
Winter assigns a value to a single array element:
[email protected] ~]# season[0]= "new_spring"Look at the array again:
[[email protected] ~]# echo ${season[*]}
New_spring Summer Autumn Winter clears the specified single array element:
[email protected] ~]# unset season[2]Clear the entire array:
[email protected] ~]# unset SEASON
4. Apply the array to the shell environment variable (2)"This is a good use!" To the original author praise one! "Use the TR command to convert a carriage return from a file into a space:
[email protected] ~]# cat/etc/shells | tr "\ n" "" ">/tmp/tmp.fileAssigns the contents of a file to an array: (the content before the first carriage return)
[email protected] ~]# read-a Shells </tmp/tmp.file To View array assignment conditions:
[[email protected] ~]# Set | grep "Shells"
shells= ([0]= "/bin/sh" [1]= "/bin/bash" [2]= "/sbin/nologin" [3]= "/bin/tcsh" [4]= "/bin/csh" [5]= "/bin/ksh")
Linux Shell Programming (3): arrays
