bash - 用 Bash 变量替换 sed

Question

我正在尝试在 Bash 脚本中使用 sed 更改文本文件中的值，

sed 's/draw($prev_number;n_)/draw($number;n_)/g' file.txt > tmp

这将在 for 循环中。为什么它不起作用？

Answer 1

' 中的变量不会在 Bash 中被替换。要进行字符串替换(或插值，如果您熟悉 Perl)，您需要将其更改为使用双引号 " 而不是单引号:

# Enclose the entire expression in double quotes
$ sed "s/draw($prev_number;n_)/draw($number;n_)/g" file.txt > tmp

# Or, concatenate strings with only variables inside double quotes
# This would restrict expansion to the relevant portion
# and prevent accidental expansion for !, backticks, etc.
$ sed 's/draw('"$prev_number"';n_)/draw('"$number"';n_)/g' file.txt > tmp

# A variable cannot contain arbitrary characters
# See link in the further reading section for details
$ a='foo
bar'
$ echo 'baz' | sed 's/baz/'"$a"'/g'
sed: -e expression #1, char 9: unterminated `s' command

进一步阅读:

• Difference between single and double quotes in Bash
• Is it possible to escape regex metacharacters reliably with sed
• Using different delimiters for sed substitute command
• 除非您需要它在不同的文件中，否则您可以使用 -i flag to change the file in place