Bash String操作

• 獲取string長度

${#var}

例如
a="I am long"
echo ${#a}

切取字段
${string:position:length}或者
${string:position}
例如：
var="Welcome to the geekstuff"

echo ${var:15}
echo ${var:15:4}
刪除字符串
${string#substring} 刪除頭部開始計算的第一個符合要求的最短字符串
${string%substring} 刪除尾部開始計算的第一個符合要求的最短字符串

filename="bash.string.txt"

echo ${filename#*.}
echo ${filename%.*}

$ ./shortest.sh
After deletion of shortest match from front: string.txt
After deletion of shortest match from back: bash.string

${string##substring} 刪除頭部開始計算的符合要求的最長字符串
${string%%substring} 刪除尾部開始計算的符合要求的最長字符串
filename="bash.string.txt"

echo "After deletion of longest match from front:" ${filename##*.}
echo "After deletion of longest match from back:" ${filename%%.*}

$ ./longest.sh
After deletion of longest match from front: txt


After deletion of longest match from back: bash
獲取子串索引：
expr index $string $substring

stringZ=abcABC123ABCabc
# 123456 ...
echo `expr index "$stringZ" C12` # 6
# C position.

echo `expr index "$stringZ" 1c` # 3

# 'c' (in #3 position) matches before '1'.