使用 sed 将模式转义到另一个 sed

Question

我想要一种使用 sed 命令进行替换的方法，该命令转义要在另一个 sed 命令中使用的“模式”（字符串）。 此转义过程必须包括对多行字符串模式的处理。

为了说明，我提供了下面的代码。它工作得很好（到目前为止测试良好），但是当我们有多行字符串时会失败（参见“STRING_TO_ESCAPE”）。

#!/bin/bash

# Escape TARGET_STRING.
read -r -d '' STRING_TO_ESCAPE <<'HEREDOC'
    $N = "magic_quotes_gpc = <b>"._("On")."</b>";
    $D = _("Increase your server security by setting magic_quotes_gpc to 'on'. PHP will escape all quotes in strings in this case."); 
    $S = _("Search for 'magic_quotes_gpc' in your php.ini and set it to 'On'."); 
    $R = ini_get('magic_quotes_gpc'); 
    $M = TRUE;
    $this->config_checks[] = array("NAME" => $N , "DESC" => $D , "RESULT" => $R , "SOLUTION" => $S , "MUST" => $M );
HEREDOC
ESCAPED_STRING=$(echo "'${STRING_TO_ESCAPE}'" | sed 's/[]\/$*.^|[]/\\&/g')
ESCAPED_STRING=${ESCAPED_STRING%?}
TARGET_STRING=${ESCAPED_STRING#?}

# NOTE: The single quotes in "'${STRING_TO_ESCAPE}'" serve to prevent spaces 
# being "lost" at the beginning and end of the string! The manipulations with 
# "ESCAPED_STRING" are used to remove them. When we use sed with the file being 
# input (flag "-i") this problem does not occur.

# Escape REPLACE_STRING.
read -r -d '' STRING_TO_ESCAPE <<'HEREDOC'
    /* NOTE: "Magic_quotes_gpc" is no longer required. We taught GOsa2 to deal with it (see /usr/share/gosa/html/main.php). By Questor */
    /* Automatic quoting must be turned on */
    /* $N = "magic_quotes_gpc = <b>"._("On")."</b>";
    $D = _("Increase your server security by setting magic_quotes_gpc to 'on'. PHP will escape all quotes in strings in this case."); 
    $S = _("Search for 'magic_quotes_gpc' in your php.ini and set it to 'On'."); 
    $R = ini_get('magic_quotes_gpc'); 
    $M = TRUE;
    $this->config_checks[] = array("NAME" => $N , "DESC" => $D , "RESULT" => $R , "SOLUTION" => $S , "MUST" => $M ); */
HEREDOC
ESCAPED_STRING=$(echo "'${STRING_TO_ESCAPE}'" | sed 's/[]\/$*.^|[]/\\&/g')
ESCAPED_STRING=${ESCAPED_STRING%?}
REPLACE_STRING=${ESCAPED_STRING#?}

# Do the replace.
STRING_TO_MODIFY=$(cat file_name.txt)
MODIFIED_STRING=$(echo "'${STRING_TO_MODIFY}'" | sed 's/$TARGET_STRING/$REPLACE_STRING/g')
MODIFIED_STRING=${MODIFIED_STRING%?}
MODIFIED_STRING=${MODIFIED_STRING#?}

echo "$MODIFIED_STRING"

谢谢！ =D

Answer 1

此转义过程必须包括对多行字符串模式的处理。

我认为你找错树了。如果您尝试匹配多行模式，那么最重要的问题不是如何转义该模式，而是如何编写能够成功匹配任何内容的 sed 脚本。

问题是sed 一次读取一行输入。有多种方法可以收集多行并对此类集合进行操作，但您需要在程序中明确执行此操作。因此，sed 是尝试匹配任意多行文本的糟糕选择。为了使您的任务可行，您会想知道该模式将包含多少行，以便编写您的 sed 程序来专门针对它。即便如此，这对 Perl 来说可能是一个更好的工作。

更新：

因为我喜欢sed，但是，这里有一个示例，说明如何编写匹配多行模式的sed 程序：

#!/bin/sed -f
# Build up a three-line window in the pattern space
:a
/\(.*\
\)\{2\}/! { N; ba; }

# A(nother) multiline pattern.  If the pattern fails to match then the
# first line of the pattern space is printed and deleted, then
# we loop back to reload.
/^The\
quick\
brown$/! { P; D; ba; }

# Do whatever we want to do in the event of a match
s/brown/red/

# If control reaches here then the whole pattern space is printed,
# and if any input lines remain then we start again from the beginning
# with an initially-empty pattern space.

示例输入：

$ ./ml.sed <<EOF
The
quick
brown
fox          
jumped over
the lazy dog.
EOF

输出：

The
quick
red
fox
jumped over
the lazy dog.

请注意，换行符与普通字符匹配，但出于句法原因，模式或替换文本中的文字换行符需要以正常方式转义。

更新 2：

这是替换三行序列外观的变体

brown
fox          
jumped over

三行序

red
pig          
is fat

。当然，还有很多其他方法可以使用 sed 完成同样的事情，对于您的特定目的，其他方法之一可能比这更可取。

#!/bin/sed -f
:a
/\(.*\
\)\{2\}/! { N; ba; }

/^brown\
fox\
jumped over$/! { P; D; ba; }

s/.*/red\
pig\
is fat/