在UNIX中汇总多个文件

Question

I am trying to summarize multiple files parallely. As I display variable it contains null

a=`cat file1| sort | uniq | wc -l` & # file1 have 200k records

b=`cat file2|sort | uniq | wc -l` & # file1 have 240k records

sh -x process1.sh &

wait

echo a=$a

echo b=$b

Output

a=

b=

Expected Output

a=200000

b=240000

Answer 1

Try:

a=`cat file1| sort | uniq | wc -l &` 

instead of:

a=`cat file1| sort | uniq | wc -l` & 

Also there are several minor problems:

1. useless cat.

2. using backticks instead of $(...)

3. no double quotes around variable

Refactored working version:

#!/bin/bash 

a=$(sort file1 | uniq | wc -l &)
b=$(sort file2 | uniq | wc -l &)
wait
echo a="$a"
echo b="$b"