bash 如何检查 sed 命令是否替换了某个字符串？
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How to check if the sed command replaced some string?
提问by Lukap
This command replaces the old string with the new one if the one exists.
如果旧字符串存在，此命令将用新字符串替换旧字符串。
sed "s/$OLD/$NEW/g" "$source_filename" > $dest_filename
How can I check if the replacement happened ? (or how many times happened ?)
我如何检查是否发生了更换？（或者发生了多少次？）
采纳答案by Gilles Quenot
sedis not the right tool if you need to count the substitution, awkwill fit better your needs :
如果您需要计算替换，sed不是正确的工具，awk将更适合您的需求：
awk -v OLD=foo -v NEW=bar '
(OLD=foo NEW=bar perl -pe '
$count += s/$ENV{OLD}/$ENV{NEW}/g;
END{print "$count substitutions occured.\n"}
' "$source_filename"
~ OLD) {gsub(OLD, NEW); count++}1
END{print count " substitutions occured."}
' "$source_filename"
This latest solution counts only the number of lines substituted. The next snippet counts all substitutions with perl. This one has the advantage to be clearer than awkand we keep the syntax of sedsubstitution :
这个最新的解决方案只计算被替换的行数。下一个片段使用perl计算所有替换。这个优点比awk我们保留sed替换的语法更清晰：
grep -o 'pattern'|wc -l file && sed 's/pattern/rep/g' oldfile > newfile
Edit
编辑
Thanks to williamwho had found the $count += s///gtrick to count the number of substitutions (even or not on the same line)
感谢威廉找到了$count += s///g计算替换次数的技巧（即使在同一行或不在同一行）
回答by Kent
If it is free for you to choose other tool, like awk, (as @sputnick suggested), go with other tools. Awk could count how many times the pattern matched.
如果您可以免费选择其他工具，例如 awk，（如@sputnick 建议的那样），请使用其他工具。awk 可以计算模式匹配的次数。
sed itself cannot count replacement, particularly if you use /gflag. however if you want to stick to sedand know the replacement times there is possibilities:
sed 本身不能算替换，特别是如果您使用/g标志。但是，如果您想坚持sed并知道更换时间，则有可能：
One way is
一种方法是
cat file|tee >(grep -o 'pattern'|wc -l)|(sed 's/pattern/replace/g' >newfile)
you could also do it with tee
你也可以用T 恤做到这一点
kent$ cat file
abababababa
aaaaaa
xaxaxa
kent$ cat file|tee >(grep -o 'a'|wc -l)|(sed 's/a/-/g' >newfile)
15
kent$ cat newfile
-b-b-b-b-b-
------
x-x-x-
see this small example:
看这个小例子：
awk 'END{print t, "substitutions"} {t+=gsub(old,new)}1' old="foo" new="bar" file
回答by Scrutinizer
This awkshould count the total number of substitutions instead of the number of lines where substitutions took place:
这awk应该计算替换的总数，而不是发生替换的行数：
awk -v s="OLD" -v c="NEW" '{count+=gsub(s,c); }1
END{print count "numbers"}
' opfilename
回答by Narayan
this worked for me.
这对我有用。
##代码##