我试图替换特定单词后的文本,但sed
正在更改整行。提取特定单词后的一个单词
输入文件:样本.txt
My Hostname:internal is valid.
some log file entries
some log file entries
输出:
My Hostname:mmphate
some log file entries
some log file entries
预期输出:
My Hostname:mmphate is valid.
some log file entries
some log file entries
我编写了下面的脚本,该脚本在Hostname:
我只想更改一个单词后更改所有单词Hostname:
#!/usr/bin/env bash
HOST=$(curl -s 169.254.169.254/latest/meta-data/local-hostname)
while getopts ih opt
do
case $opt in
i)
;;
h)
sed -e "s/Hostname:.*/Hostname:$HOST/g" sample.txt
echo "Updated Hostname: $HOST"
;;
esac
done
答案1
当您对右旋您s///
需要注意对输入进行正确的转义,因为它们可能是特殊的sed
,因此会导致错误,或者更糟糕的是,没有错误,但结果完全是意外的。例如,考虑一下如果您$HOST
包含 & 符号&
或会发生什么/
。
# definitions
TAB=`echo 'x' | tr 'x' '\011'`; # tab
SPC=`echo 'x' | tr 'x' '\040'`; # space
eval "`echo 'n=qsq' | tr 'qs' '\047\012'`"; # newline
# construct regexes
s="[$SPC$TAB]"; # spc/tab regex
S="[^$SPC$TAB]"; # nonwhitespace regex
# perform the escape operation
esc() {
set -- "${1//\\/\\\\}" # escape backslash to prevent it from dissolving
set -- "${1//\//\\\/}" # escape forward slash to prevent from clashing with delimiters
set -- "${1//&/\\&}" # escape ampersand since it has a specific meaning rhs of s//
set -- "${1//\"/\\\"}" # escape double quotes in an interpolation
set -- "${1//$n/\\$n}" # escape newlines
printf '%s\n' "$@"
}
# grab the hostname
HOST=$(curl -s 169.254.169.254/latest/meta-data/local-hostname)
# escape hostname to enable it to be used seamlessly on the rhs of s///
host_esc=$(esc "$HOST")
# and then...
sed -e "s/\(${s}Hostname\):$S$S*/\1:$host_esc/g" sample.txt
答案2
.*
与该行其余部分的所有内容匹配,因此所有内容都被替换。如果您想将所有内容替换到下一个空格,那么您需要[^ ] instead of
。`
答案3
您的问题不可重现:
$ name="george"
$ echo "My Hostname:internal is valid." |sed "s/internal/$name/g"
My Hostname:george is valid.
如果该词internal
也存在于下面的日志条目中,My Hostname
那么您可以使用如下内容:
$ sed -r "s/(My Hostname:)(internal)/\1$name/g" file4
My Hostname:george is valid.
internal log entry
log internal entry
如果您没有GNU Sed
或sed
由于某种原因无法按预期工作,对于这种简单的替换,您可以随时切换到perl
在任何地方都以相同方式工作的方法:
$ cat file4
My Hostname:internal is valid.
internal log entry
log internal entry
$ perl -pe "s/(My Hostname:)(internal)/\1$name/g" file4
My Hostname:george is valid.
internal log entry
log internal entry
如果需要,sed 和 perl 都可以结合起来-i
进行就地编辑。