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 $text > filename
我期待的是这样的:
this is line one
this is line two
this is line three
但我明白了:
this is line one
this is line two
this is line three
我确信在每个\n之后没有空间，但额外的空间是如何出来的?
当前回答
如果你试图将字符串转换为变量，另一种简单的方法是这样的:
USAGE=$(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。
其他回答
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。
如果你把它放在下面，它就会工作:
AA='first line
\nsecond line
\nthird line'
echo $AA
output:
first line
second line
third line
我听到这个答案，但也想把它输送到另一个命令。给出的答案是正确的，但如果有人想要管道它，您需要在像这样的多行字符串之前管道它
echo | tee /tmp/pipetest << EndOfMessage
This is line 1.
This is line 2.
Line 3.
EndOfMessage
这将允许您拥有多行字符串，但也可以将其放在后续命令的stdin中。
我发现了更多的解决方案，因为我想有每一行适当缩进:
You may use echo: echo "this is line one" \ "\n""this is line two" \ "\n""this is line three" \ > filename It does not work if you put "\n" just before \ on the end of a line. Alternatively, you can use printf for better portability (I happened to have a lot of problems with echo): printf '%s\n' \ "this is line one" \ "this is line two" \ "this is line three" \ > filename Yet another solution might be: text='' text="${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' "$text"
这里只提一个简单的单行连接，因为它有时很有用。
# for bash
v=" guga "$'\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
