我有一个shell脚本与这段代码:
var=`hg st -R "$path"`
if [ -n "$var" ]; then
echo $var
fi
但是条件代码总是执行，因为hg st总是打印至少一个换行符。
是否有一个简单的方法从$var中剥离空白(如PHP中的trim())?
or
有没有处理这个问题的标准方法?
我可以使用sed或AWK，但我认为有一个更优雅的解决方案来解决这个问题。
当前回答
# 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 "$1")")"
}
其他回答
这将删除字符串中的所有空格，
VAR2="${VAR2//[[:space:]]/}"
/替换字符串中第一次出现的空格和//所有出现的空格。也就是说，所有的空格都被- nothing取代
我将简单地使用sed:
function trim
{
echo "$1" | sed -n '1h;1!H;${;g;s/^[ \t]*//g;s/[ \t]*$//g;p;}'
}
a)单行字符串使用示例
string=' wordA wordB wordC wordD '
trimmed=$( trim "$string" )
echo "GIVEN STRING: |$string|"
echo "TRIMMED STRING: |$trimmed|"
输出:
GIVEN STRING: | wordA wordB wordC wordD |
TRIMMED STRING: |wordA wordB wordC wordD|
b)多行字符串使用示例
string=' wordA
>wordB<
wordC '
trimmed=$( trim "$string" )
echo -e "GIVEN STRING: |$string|\n"
echo "TRIMMED STRING: |$trimmed|"
输出:
GIVEN STRING: | wordAA
>wordB<
wordC |
TRIMMED STRING: |wordAA
>wordB<
wordC|
c)最后说明: 如果你不喜欢使用函数，对于单行字符串，你可以简单地使用“更容易记住”的命令，比如:
echo "$string" | sed -e 's/^[ \t]*//' | sed -e 's/[ \t]*$//'
例子:
echo " wordA wordB wordC " | sed -e 's/^[ \t]*//' | sed -e 's/[ \t]*$//'
输出:
wordA wordB wordC
在多行字符串上使用上述方法也可以，但请注意，它也会切断任何尾随/前导内部多行空间，就像GuruM在评论中注意到的那样
string=' wordAA
>four spaces before<
>one space before< '
echo "$string" | sed -e 's/^[ \t]*//' | sed -e 's/[ \t]*$//'
输出:
wordAA
>four spaces before<
>one space before<
所以如果你介意保留这些空格，请使用我回答开头的函数!
d)解释sed语法“find and replace”在函数trim中使用的多行字符串:
sed -n '
# If the first line, copy the pattern to the hold buffer
1h
# If not the first line, then append the pattern to the hold buffer
1!H
# If the last line then ...
$ {
# Copy from the hold to the pattern buffer
g
# Do the search and replace
s/^[ \t]*//g
s/[ \t]*$//g
# print
p
}'
# 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")")"
}
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='$result'" >&2
done
}
enum | xcheck
我总是用sed来做
var=`hg st -R "$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。
