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
var=' a b c '
trimmed=$(echo $var)
其他回答
剥离一个前导和一个后导空间
trim()
{
local trimmed="$1"
# Strip leading space.
trimmed="${trimmed## }"
# Strip trailing space.
trimmed="${trimmed%% }"
echo "$trimmed"
}
例如:
test1="$(trim " one leading")"
test2="$(trim "one trailing ")"
test3="$(trim " one leading and one trailing ")"
echo "'$test1', '$test2', '$test3'"
输出:
'one leading', 'one trailing', 'one leading and one trailing'
去掉所有前导和尾随空格
trim()
{
local trimmed="$1"
# Strip leading spaces.
while [[ $trimmed == ' '* ]]; do
trimmed="${trimmed## }"
done
# Strip trailing spaces.
while [[ $trimmed == *' ' ]]; do
trimmed="${trimmed%% }"
done
echo "$trimmed"
}
例如:
test4="$(trim " two leading")"
test5="$(trim "two trailing ")"
test6="$(trim " two leading and two trailing ")"
echo "'$test4', '$test5', '$test6'"
输出:
'two leading', 'two trailing', 'two leading and two trailing'
var=" a b "
echo "$(set -f; echo $var)"
>a b
这里有一个trim()函数，用于修整和规范化空白
#!/bin/bash
function trim {
echo $*
}
echo "'$(trim " one two three ")'"
# 'one two three'
还有一种使用正则表达式的变体。
#!/bin/bash
function trim {
local trimmed="$@"
if [[ "$trimmed" =~ " *([^ ].*[^ ]) *" ]]
then
trimmed=${BASH_REMATCH[1]}
fi
echo "$trimmed"
}
echo "'$(trim " one two three ")'"
# 'one two three'
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
#!/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]
#[]
