Shell脚本中的cut命令

Question

My shell script look like this

 i="10 ID:794 A:TX-SPN S:0"
 A=`echo $i | cut -d" " -f 3| cut -d":" -f2`  # gives TX-SPN
 ID=`echo $i | cut -d" " -f 2|cut -d":" -f2`  # gives 794 
 sZeroCount=`echo $i | cut -d" " -f 1`  # gives  10

by above commands,I am able to get the values for A,ID,sZeroCount variables, since the value for i contains only one entry, value of i not limited to 1 it may go upto 1000. Is there any better approach in which I can obtain those values.

Answer 1

With an array. Split string i with separator space and : to array a :

i="10 ID:794 A:TX-SPN S:0"
IFS=" :" a=($i)
echo "${a[4]}" # TX-SPN
echo "${a[2]}" # 794
echo "${a[0]}" # 10

With chepner's bugfix:

i="10 ID:794 A:TX-SPN S:0"
IFS=": " read -a a <<< "$i"
echo "${a[4]}" # TX-SPN
echo "${a[2]}" # 794
echo "${a[0]}" # 10

Answer 2

With this piece of code you can convert your line into a proper associative array:

declare -A dict
for token in START:$i  # choose a value for START that is not a key
do
  IFS=: read key value <<< "$token"
  dict["$key"]=$value
done

You can dump the result using declare -p dict :

declare -A dict='([A]="TX-SPN" [S]="0" [ID]="794" [START]="10" )'

And you can access the contents eg using this: echo "${dict[A]}"

TX-SPN

The start value (the 10 in your example) can be accessed as "${dict[START]}" . Choose a value for START that doesn't appear as key in your input.

If you want to iterate over a lot of lines like your $i , you can do it like this:

while read i
do
  declare -A dict
  # ... add code from above ...
done < input_file

The advantage of using associative arrays is that this way you can access your values in a much more understandable way, ie by using the keys instead of some arbitrary indexes which can easily be mixed up and which need constant maintenance when changing your code.