我想写一些预定义的文本与以下文件:
text="this is line one\n
this is line two\n
this is line three"
echo -e $text > filename
我期待的是这样的:
this is line one
this is line two
this is line three
但我明白了:
this is line one
this is line two
this is line three
我确信在每个\n之后没有空间，但额外的空间是如何出来的?
当前回答
有很多方法可以做到这一点。对我来说，将缩进的字符串输送到sed中效果很好。
printf_strip_indent() {
printf "%s" "$1" | sed "s/^\s*//g"
}
printf_strip_indent "this is line one
this is line two
this is line three" > "file.txt"
这个答案是基于Mateusz Piotrowski的回答，但做了一些改进。
其他回答
我发现了更多的解决方案，因为我想有每一行适当缩进:
You may use echo: echo "this is line one" \ "\n""this is line two" \ "\n""this is line three" \ > filename It does not work if you put "\n" just before \ on the end of a line. Alternatively, you can use printf for better portability (I happened to have a lot of problems with echo): printf '%s\n' \ "this is line one" \ "this is line two" \ "this is line three" \ > filename Yet another solution might be: text='' text="${text}this is line one\n" text="${text}this is line two\n" text="${text}this is line three\n" printf "%b" "$text" > filename or text='' text+="this is line one\n" text+="this is line two\n" text+="this is line three\n" printf "%b" "$text" > filename Another solution is achieved by mixing printf and sed. if something then printf '%s' ' this is line one this is line two this is line three ' | sed '1d;$d;s/^ //g' fi It is not easy to refactor code formatted like this as you hardcode the indentation level into the code. It is possible to use a helper function and some variable substitution tricks: unset text _() { text="${text}${text+ }${*}"; } # That's an empty line which demonstrates the reasoning behind # the usage of "+" instead of ":+" in the variable substitution # above. _ "" _ "this is line one" _ "this is line two" _ "this is line three" unset -f _ printf '%s' "$text"
Echo在传递给它的参数之间添加空格。$text受变量扩展和单词分割的影响，所以你的echo命令相当于:
echo -e "this" "is" "line" "one\n" "this" "is" "line" "two\n" ...
你可以看到在“this”之前加了一个空格。你可以删除换行符，并引用$text来保留换行符:
text="this is line one
this is line two
this is line three"
echo "$text" > filename
或者你可以使用printf，它比echo更健壮和可移植:
printf "%s\n" "this is line one" "this is line two" "this is line three" > filename
在支持大括号展开的bash中，你甚至可以这样做:
printf "%s\n" "this is line "{one,two,three} > filename
下面是我喜欢的方式来分配一个多行字符串的变量(我认为它看起来不错)。
read -r -d '' my_variable << \
_______________________________________________________________________________
String1
String2
String3
...
StringN
_______________________________________________________________________________
在这两种情况下，下划线的数量是相同的(这里是80)。
如果你把它放在下面，它就会工作:
AA='first line
\nsecond line
\nthird line'
echo $AA
output:
first line
second line
third line
有很多方法可以做到这一点。对我来说，将缩进的字符串输送到sed中效果很好。
printf_strip_indent() {
printf "%s" "$1" | sed "s/^\s*//g"
}
printf_strip_indent "this is line one
this is line two
this is line three" > "file.txt"
这个答案是基于Mateusz Piotrowski的回答，但做了一些改进。
