☰

使用从 bash 调用的 awk 在文件中添加一行

tag-icon • tag-icon bash awk
使用从 bash 调用的 awk 在文件中添加一行

我有这个文件

127.0.0.1   localhost

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

我想使用 awk 在模式之后/之前添加一行127.0.0.1。 Pattern 和 line 是 bash 变量。

#!/bin/bash

file="test.txt"
pattern='127.0.0.1'
line='127.0.1.1   cent.centurian.com   centurian'

awk -vpattern="$pattern" -vline="$line" '/pattern/{print;print line;next}1' "$file"

不起作用...

答案1

sed更简单：

sed "/$pattern/a\
$line" "$file"

输出：

127.0.0.1   localhost
127.0.1.1   cent.centurian.com   centurian

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

GNU sed允许上述的单行版本：

sed $file -e "/$pattern/a $line"

...并输出$line 前 $pattern，改变a（待定）到一个i（插入）：

sed $file -e "/$pattern/i $line"

答案2

关闭。这会寻找（字面意思）模式pattern。

您需要使用$0 ~ pattern来匹配变量。

$ pattern='127.0.0.1'
$ line='127.0.1.1   cent.centurian.com   centurian'
$ awk -vpattern="$pattern" -vline="$line" '$0 ~ pattern {print; print line; next} 1' $file | head -2
127.0.0.1   localhost
127.0.1.1   cent.centurian.com   centurian

答案3

刚刚做了一个函数来执行此操作：

################################################################################
## Adds a line in a file.                                                     ##
#------------------------------------------------------------------------------#
# Given the arguments:                                                         #
# 1st: file                                                                    #
# 2nd: string to find                                                          #
# 3rd: line to add                                                             #
# 4th: 'b' for before, 'a' for after.                                          #
# It adds a line before or after the line containing the search string.        #
################################################################################
function addLineInFileOnString() {
   local file pattern line where tmp
   file="$1"
   pattern="$2"
   line="$3"
   where="$4"
   tmp="$( cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 8 | head -n 1 )"
   tmp='tmp.'$tmp

   if [[ $where == 'b' ]]; then
      awk -v pattern="$pattern" -v line="$line" '$0 ~ pattern {print line; print; next} 1' "$file" | tee 1>/dev/null $tmp
   elif [[ $where == 'a' ]]; then
      awk -v pattern="$pattern" -v line="$line" '$0 ~ pattern {print; print line; next} 1' "$file" | tee 1>/dev/null $tmp
   fi

   [[ -e $tmp ]] && cp "$tmp" "$file" && rm "$tmp"
}

答案4

在匹配行之前：

awk -v line='127.0.1.1   cent.centurian.com   centurian' '/127\.0\.0\.1/ \
        { printf "%s\n%s\n", line, $0; next }; 1' file.txt

匹配行之后：

awk -v line='127.0.1.1   cent.centurian.com   centurian' '/127\.0\.0\.1/ \
        { printf "%s\n%s\n", $0, line; next }; 1' file.txt

  • /127\.0\.0\.1/与模式匹配

  • printf如果模式匹配，则根据变量line是在匹配行之前还是之后打印所需的格式化输出

例子：

$ cat file.txt                                                                                                              
127.0.0.1   localhost

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

$ awk -v line='127.0.1.1   cent.centurian.com   centurian' '/127\.0\.0\.1/ { printf "%s\n%s\n", $0, line; next }; 1' file.txt
127.0.0.1   localhost
127.0.1.1   cent.centurian.com   centurian

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

$ awk -v line='127.0.1.1   cent.centurian.com   centurian' '/127\.0\.0\.1/ { printf "%s\n%s\n", line, $0; next }; 1' file.txt
127.0.1.1   cent.centurian.com   centurian
127.0.0.1   localhost

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

相关内容