在BASH中有几个不同的选项:

line=${line##+([[:space:]])}    # strip leading whitespace;  no quote expansion!
line=${line%%+([[:space:]])}   # strip trailing whitespace; no quote expansion!
line=${line//[[:space:]]/}   # strip all whitespace
line=${line//[[:space:]]/}   # strip all whitespace

line=${line//[[:blank:]]/}   # strip all blank space

前两个需要预先设置/启用extglob:

shopt -s extglob  # bash only

注意:引号内的变量展开打破了前两个例子!

这里详细介绍了POSIX括号表达式的模式匹配行为。如果您正在使用更现代/可黑客的shell，例如Fish，则有用于字符串修剪的内置函数。

Use:

trim() {
    local orig="$1"
    local trmd=""
    while true;
    do
        trmd="${orig#[[:space:]]}"
        trmd="${trmd%[[:space:]]}"
        test "$trmd" = "$orig" && break
        orig="$trmd"
    done
    printf -- '%s\n' "$trmd"
}

它适用于各种空格，包括换行符， 不需要修改shop。 它保留内部空白，包括换行符。

单元测试(用于手动检查):

#!/bin/bash

. trim.sh

enum() {
    echo "   a b c"
    echo "a b c   "
    echo "  a b c "
    echo " a b c  "
    echo " a  b c  "
    echo " a  b  c  "
    echo " a      b  c  "
    echo "     a      b  c  "
    echo "     a  b  c  "
    echo " a  b  c      "
    echo " a  b  c      "
    echo " a N b  c  "
    echo "N a N b  c  "
    echo " Na  b  c  "
    echo " a  b  c N "
    echo " a  b  c  N"
}

xcheck() {
    local testln result
    while IFS='' read testln;
    do
        testln=$(tr N '\n' <<<"$testln")
        echo ": ~~~~~~~~~~~~~~~~~~~~~~~~~ :" >&2
        result="$(trim "$testln")"
        echo "testln='$testln'" >&2
        echo "result='$result'" >&2
    done
}

enum | xcheck

这就是我所做的，结果完美而简单:

the_string="        test"
the_string=`echo $the_string`
echo "$the_string"

输出:

test

数组赋值在内部字段分隔符(默认为空格/制表符/换行符)上展开参数拆分。

words=($var)
var="${words[@]}"

我总是用sed来做

  var=`hg st -R "$path" | sed -e 's/  *$//'`

如果有更优雅的解决方案，我希望有人能发布出来。

答案有很多，但我仍然认为我刚刚写的剧本值得一提，因为:

it was successfully tested in the shells bash/dash/busybox shell it is extremely small it doesn't depend on external commands and doesn't need to fork (->fast and low resource usage) it works as expected: it strips all spaces and tabs from beginning and end, but not more important: it doesn't remove anything from the middle of the string (many other answers do), even newlines will remain special: the "$*" joins multiple arguments using one space. if you want to trim & output only the first argument, use "$1" instead if doesn't have any problems with matching file name patterns etc

脚本:

trim() {
  local s2 s="$*"
  until s2="${s#[[:space:]]}"; [ "$s2" = "$s" ]; do s="$s2"; done
  until s2="${s%[[:space:]]}"; [ "$s2" = "$s" ]; do s="$s2"; done
  echo "$s"
}

用法:

mystring="   here     is
    something    "
mystring=$(trim "$mystring")
echo ">$mystring<"

输出:

>here     is
    something<