Remove whitespace characters from Bash variables - The Road to Dreaming

echo processing

echo ${#var}    用于获取字符串变量的长度

echo -n ${var}  -n 使 echo 不打印末尾的换行符

echo and xargs handling

# 示例
#! /bin/bash
var="  test  "
var=$(echo $var | xargs)
echo "|${var}|"

xargs 会删除字符串首尾的空白符，还会将字符串中间连续的多个空格压缩为单个空格

Bash built-in functions and wildcards

# 示例
#! /bin/bash
var="    abc    "
# 删除前导空白字符
var="${var#"${var%%[![:space:]]*}"}"
# 删除尾部空白字符
var="${var%"${var##*[![:space:]]}"}"   
printf '%s\n' "===$var==="

for collection purposes