# 方法1:
#!/bin/bash
string="a k g j a a a k a j j j a h h"
echo $string
for i in `echo $string`
do
if [[ $i == a ]]
then
n=`expr $n + 1`
fi
done
echo $n
## Note;本方法处理字符串列表更便捷
# 方法2:
#!/bin/bash
string="a k g j a a a k a j j j a h h"
#string="akgjaaakajjjahh"
a=`echo $string |sed "s/\ //g" |wc -m`
echo $a
b=`echo $string |awk -F"a" '{for (i=1;i<=NF;i++)printf("%s ", $i);print ""}'|sed "s/\ //g" |wc -m`
echo $b
echo `echo "$a-$b" |bc`
## Note:本方法可以处理字符串及字符串列表
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