Python有一个函数strip()，它的工作原理与PHP的trim()相同，因此我们可以使用一点内联Python来创建一个易于理解的实用程序:

alias trim='python -c "import sys; sys.stdout.write(sys.stdin.read().strip())"'

这将删除开头和结尾的空白(包括换行符)。

$ x=`echo -e "\n\t   \n" | trim`
$ if [ -z "$x" ]; then echo hi; fi
hi

#Execute this script with the string argument passed in double quotes !! 
#var2 gives the string without spaces.
#$1 is the string passed in double quotes
#!/bin/bash
var2=`echo $1 | sed 's/ \+//g'`
echo $var2

# Strip leading and trailing white space (new line inclusive).
trim(){
    [[ "$1" =~ [^[:space:]](.*[^[:space:]])? ]]
    printf "%s" "$BASH_REMATCH"
}

OR

# Strip leading white space (new line inclusive).
ltrim(){
    [[ "$1" =~ [^[:space:]].* ]]
    printf "%s" "$BASH_REMATCH"
}

# Strip trailing white space (new line inclusive).
rtrim(){
    [[ "$1" =~ .*[^[:space:]] ]]
    printf "%s" "$BASH_REMATCH"
}

# Strip leading and trailing white space (new line inclusive).
trim(){
    printf "%s" "$(rtrim "$(ltrim "$1")")"
}

OR

# Strip leading and trailing specified characters.  ex: str=$(trim "$str" $'\n a')
trim(){
    if [ "$2" ]; then
        trim_chrs="$2"
    else
        trim_chrs="[:space:]"
    fi

    [[ "$1" =~ ^["$trim_chrs"]*(.*[^"$trim_chrs"])["$trim_chrs"]*$ ]]
    printf "%s" "${BASH_REMATCH[1]}"
}

OR

# Strip leading specified characters.  ex: str=$(ltrim "$str" $'\n a')
ltrim(){
    if [ "$2" ]; then
        trim_chrs="$2"
    else
        trim_chrs="[:space:]"
    fi

    [[ "$1" =~ ^["$trim_chrs"]*(.*[^"$trim_chrs"]) ]]
    printf "%s" "${BASH_REMATCH[1]}"
}

# Strip trailing specified characters.  ex: str=$(rtrim "$str" $'\n a')
rtrim(){
    if [ "$2" ]; then
        trim_chrs="$2"
    else
        trim_chrs="[:space:]"
    fi

    [[ "$1" =~ ^(.*[^"$trim_chrs"])["$trim_chrs"]*$ ]]
    printf "%s" "${BASH_REMATCH[1]}"
}

# Strip leading and trailing specified characters.  ex: str=$(trim "$str" $'\n a')
trim(){
    printf "%s" "$(rtrim "$(ltrim "$1" "$2")" "$2")"
}

OR

建立在moskit的expr soulution…

# Strip leading and trailing white space (new line inclusive).
trim(){
    printf "%s" "`expr "$1" : "^[[:space:]]*\(.*[^[:space:]]\)[[:space:]]*$"`"
}

OR

# Strip leading white space (new line inclusive).
ltrim(){
    printf "%s" "`expr "$1" : "^[[:space:]]*\(.*[^[:space:]]\)"`"
}

# Strip trailing white space (new line inclusive).
rtrim(){
    printf "%s" "`expr "$1" : "^\(.*[^[:space:]]\)[[:space:]]*$"`"
}

# Strip leading and trailing white space (new line inclusive).
trim(){
    printf "%s" "$(rtrim "$(ltrim "$1")")"
}

你可以使用tr删除换行符:

var=`hg st -R "$path" | tr -d '\n'`
if [ -n $var ]; then
    echo $var
done

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

var = '  a b  '
# remove all white spaces
new=$(echo $var |  tr -d ' ')
# remove leading and trailing whitespaces
new=$(echo $var)

ab
a b