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"

对于这个目的,Heredoc听起来更方便。它用于向命令解释器程序(如ex或cat)发送多个命令

cat << EndOfMessage
This is line 1.
This is line 2.
Line 3.
EndOfMessage

<<后面的字符串表示停止的位置。

要将这些行发送到文件,请使用:

cat > $FILE <<- EOM
Line 1.
Line 2.
EOM

你也可以将这些行存储到一个变量中:

read -r -d '' VAR << EOM
This is line 1.
This is line 2.
Line 3.
EOM

这将行存储到名为VAR的变量中。

打印时,请记住变量周围的引号,否则将看不到换行符。

echo "$VAR"

更好的是,您可以使用缩进使它在代码中更加突出。这一次,只需在<<后添加一个-来阻止选项卡出现。

read -r -d '' VAR <<- EOM
    This is line 1.
    This is line 2.
    Line 3.
EOM

但是在代码中必须使用制表符而不是空格来缩进。

这里只提一个简单的单行连接,因为它有时很有用。

# for bash

v=" guga "$'\n'"   puga "

# Just for an example.
v2="bar "$'\n'"   foo "$'\n'"$v"

# Let's simplify the previous version of $v2.
n=$'\n'
v3="bar ${n}   foo ${n}$v"

echo "$v3" 

你会得到这样的结果

bar 
   foo 
 guga 
   puga 

所有前导和结尾空格将被保留

echo "$v3" > filename

如果你试图将字符串转换为变量,另一种简单的方法是这样的:

USAGE=$(cat <<-END
    This is line one.
    This is line two.
    This is line three.
END

)

如果你用制表符缩进字符串(例如,'\t'),缩进将被删除。如果使用空格缩进,则缩进将保留。

注意:最后一个右括号在另一行,这很重要。END文本必须单独出现在一行中。

我听到这个答案,但也想把它输送到另一个命令。给出的答案是正确的,但如果有人想要管道它,您需要在像这样的多行字符串之前管道它

echo | tee /tmp/pipetest << EndOfMessage
This is line 1.
This is line 2.
Line 3.
EndOfMessage

这将允许您拥有多行字符串,但也可以将其放在后续命令的stdin中。