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。
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
#!/bin/bash
function trim
{
typeset trimVar
eval trimVar="\${$1}"
read trimVar << EOTtrim
$trimVar
EOTtrim
eval $1=\$trimVar
}
# Note that the parameter to the function is the NAME of the variable to trim,
# not the variable contents. However, the contents are trimmed.
# Example of use:
while read aLine
do
trim aline
echo "[${aline}]"
done < info.txt
# File info.txt contents:
# ------------------------------
# ok hello there $
# another line here $
#and yet another $
# only at the front$
#$
# Output:
#[ok hello there]
#[another line here]
#[and yet another]
#[only at the front]
#[]
其他回答
我创建了以下函数。我不确定printf的可移植性如何,但这个解决方案的美妙之处在于,您可以通过添加更多字符代码来指定什么是“空白”。
iswhitespace()
{
n=`printf "%d\n" "'$1'"`
if (( $n != "13" )) && (( $n != "10" )) && (( $n != "32" )) && (( $n != "92" )) && (( $n != "110" )) && (( $n != "114" )); then
return 0
fi
return 1
}
trim()
{
i=0
str="$1"
while (( i < ${#1} ))
do
char=${1:$i:1}
iswhitespace "$char"
if [ "$?" -eq "0" ]; then
str="${str:$i}"
i=${#1}
fi
(( i += 1 ))
done
i=${#str}
while (( i > "0" ))
do
(( i -= 1 ))
char=${str:$i:1}
iswhitespace "$char"
if [ "$?" -eq "0" ]; then
(( i += 1 ))
str="${str:0:$i}"
i=0
fi
done
echo "$str"
}
#Call it like so
mystring=`trim "$mystring"`
我发现我需要从混乱的sdiff输出中添加一些代码来清理它:
sdiff -s column1.txt column2.txt | grep -F '<' | cut -f1 -d"<" > c12diff.txt
sed -n 1'p' c12diff.txt | sed 's/ *$//g' | tr -d '\n' | tr -d '\t'
这将删除尾随空格和其他不可见字符。
让我们定义一个包含开头、结尾和中间空格的变量:
FOO=' test test test '
echo -e "FOO='${FOO}'"
# > FOO=' test test test '
echo -e "length(FOO)==${#FOO}"
# > length(FOO)==16
如何删除tr中的所有空格(由[:space:]表示):
FOO=' test test test '
FOO_NO_WHITESPACE="$(echo -e "${FOO}" | tr -d '[:space:]')"
echo -e "FOO_NO_WHITESPACE='${FOO_NO_WHITESPACE}'"
# > FOO_NO_WHITESPACE='testtesttest'
echo -e "length(FOO_NO_WHITESPACE)==${#FOO_NO_WHITESPACE}"
# > length(FOO_NO_WHITESPACE)==12
如何仅删除前导空格:
FOO=' test test test '
FOO_NO_LEAD_SPACE="$(echo -e "${FOO}" | sed -e 's/^[[:space:]]*//')"
echo -e "FOO_NO_LEAD_SPACE='${FOO_NO_LEAD_SPACE}'"
# > FOO_NO_LEAD_SPACE='test test test '
echo -e "length(FOO_NO_LEAD_SPACE)==${#FOO_NO_LEAD_SPACE}"
# > length(FOO_NO_LEAD_SPACE)==15
如何删除尾随空格:
FOO=' test test test '
FOO_NO_TRAIL_SPACE="$(echo -e "${FOO}" | sed -e 's/[[:space:]]*$//')"
echo -e "FOO_NO_TRAIL_SPACE='${FOO_NO_TRAIL_SPACE}'"
# > FOO_NO_TRAIL_SPACE=' test test test'
echo -e "length(FOO_NO_TRAIL_SPACE)==${#FOO_NO_TRAIL_SPACE}"
# > length(FOO_NO_TRAIL_SPACE)==15
如何删除前导和尾随空格-链种子:
FOO=' test test test '
FOO_NO_EXTERNAL_SPACE="$(echo -e "${FOO}" | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')"
echo -e "FOO_NO_EXTERNAL_SPACE='${FOO_NO_EXTERNAL_SPACE}'"
# > FOO_NO_EXTERNAL_SPACE='test test test'
echo -e "length(FOO_NO_EXTERNAL_SPACE)==${#FOO_NO_EXTERNAL_SPACE}"
# > length(FOO_NO_EXTERNAL_SPACE)==14
或者,如果你的bash支持它,你可以替换echo -e "${FOO}" | sed…有了sed…<<<${FOO},像这样(用于尾随空格):
FOO_NO_TRAIL_SPACE="$(sed -e 's/[[:space:]]*$//' <<<${FOO})"
还有一个单元测试的解决方案,它从stdin中删除$IFS,并适用于任何输入分隔符(甚至$'\0'):
ltrim()
{
# Left-trim $IFS from stdin as a single line
# $1: Line separator (default NUL)
local trimmed
while IFS= read -r -d "${1-}" -u 9
do
if [ -n "${trimmed+defined}" ]
then
printf %s "$REPLY"
else
printf %s "${REPLY#"${REPLY%%[!$IFS]*}"}"
fi
printf "${1-\x00}"
trimmed=true
done 9<&0
if [[ $REPLY ]]
then
# No delimiter at last line
if [ -n "${trimmed+defined}" ]
then
printf %s "$REPLY"
else
printf %s "${REPLY#"${REPLY%%[!$IFS]*}"}"
fi
fi
}
rtrim()
{
# Right-trim $IFS from stdin as a single line
# $1: Line separator (default NUL)
local previous last
while IFS= read -r -d "${1-}" -u 9
do
if [ -n "${previous+defined}" ]
then
printf %s "$previous"
printf "${1-\x00}"
fi
previous="$REPLY"
done 9<&0
if [[ $REPLY ]]
then
# No delimiter at last line
last="$REPLY"
printf %s "$previous"
if [ -n "${previous+defined}" ]
then
printf "${1-\x00}"
fi
else
last="$previous"
fi
right_whitespace="${last##*[!$IFS]}"
printf %s "${last%$right_whitespace}"
}
trim()
{
# Trim $IFS from individual lines
# $1: Line separator (default NUL)
ltrim ${1+"$@"} | rtrim ${1+"$@"}
}
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