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删除pattern后面的n行和pattern前面的m行

tag-icon • tag-icon text-processing awk sed
删除pattern后面的n行和pattern前面的m行

笔记: 我知道这个问题：如何 grep 反向匹配并排除“之前”和“之后”行。我的不是前面引用的重复项，该问题的答案也会删除该模式，而在这个问题中，模式本身必须保留。

我试图删除模式后面的 n 行和模式之前的 m 行（不删除模式）。例如，如果文件是：

1
2
3
4
5
6
7
8
9

如果 Pattern = 5，n = 2，m = 3。则：

1
5
8
9

您能建议如何做到这一点吗？

奖金：如果我们可以在同一代码中设置 m 或 n = 0，那就太好了。例如。如果我们设置 m=0 和 n=1，在上面的例子中，我们应该得到：

1
2
3
4
5
7
8
9

答案1

为了回答您的一般情况，我们会ed根据给定的输入类型提前构建适当的代码。

 re=5 n=2 m=3
 code=$(
   prev="/$re/-$m,/$re/-1d"
   next="/$re/+1,/$re/+${n}d"
    case "$m/$n" in
       0/0) set -- ;;
       0/?*) set -- "$next" "w" ;;
       ?*/0) set -- "$prev" "w" ;;
         *) set -- "$prev" "$next" "w" ;;
    esac
    printf '%s\n' ${1+"$@"} "q" 
 ) 
 ed -s filename - <<eof
 $code
 eof

一种方法可能是：这使用ed编辑器执行相对寻址，因为这就是您的问题的中心。

 n=3 m=2 re=5
 ed -s filename - <<eof
 /$re/-$m,/$re/-1d
 .+1,.+${n}d
 wq
 eof

解释：

 1. Line 3 after var substitution becomes
            /5/-2,/5/-1
      What it does is, sitting on line which satisfies the regex /5/, it looks 2 lines behind and stops looking 1 line before the /5/ line or the current line and deletes that bunch. Remember the current line is not deleted.

   2.  Line 4, after var sub becomes
                .+1,.+3d
       . is the nickname for the current line, which in our case is /5/
       So, starting fron one line after the current upto 3 lines after the current, delete them all. Note the current line is still untouched.

  3. Line 5 is wq which means save the modified file back onto itself and quit.

For more on info google the manual for gnu ed editor.

答案2

假设您有一个文件 - numbers.list：

1
2
3
4
5
6
7
8
9

这是一个应该可以完成您所追求的任务的脚本：

#!/bin/bash
if [ -z "$1" ]; then
    echo >&2 "error: no file specified"
    exit 1
fi
if [ ! -f "$1" ]; then
    echo >&2 "error: $1 is not a file"
    exit 1
fi
if [ -z "$2" ]; then
    echo >&2 "error: no pattern specified"
    exit 1
fi
grep "$2" "$1" >/dev/null 2>&1
if [ ! 0 -eq "$?" ]; then
    echo >&2 "error: pattern $2 not found in $1"
    exit 1
fi
MATCH_FILE="$1"
MATCH_PATTERN="$2"
MATCH_DELETE_AFTER=0
MATCH_DELETE_BEFORE=0
if [ ! -z "$3" ]; then
    MATCH_DELETE_AFTER="$3"
fi
if [ ! -z "$4" ]; then
    MATCH_DELETE_BEFORE="$4"
fi
MATCH_FILE_LINE="$( grep -n "$2" "$1" | cut -d: -f1 )"
#
# print matching `head` minus MATCH_DELETE_BEFORE lines
cat "$1" \
    | head -n "$( expr "$MATCH_FILE_LINE" - "$MATCH_DELETE_BEFORE" - 1 )"
#
# print matching line
cat "$1" \
    | head -n "$MATCH_FILE_LINE" \
    | tail -n 1
#
# print matching `tail` minus MATCH_DELETE_AFTER lines
cat "$1" \
    | tail -n "$( expr "$( wc -l "$1" | cut -d' ' -f1 )" - "$MATCH_FILE_LINE" - "$MATCH_DELETE_AFTER" )"

用法示例： ./matching.sh numbers.list 5 2 3

笔记：expr如果计算负值，则此解决方案将无法按预期工作- 如果您想实施检查以避免这种行为，则由您决定。

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