sed 删除匹配行的指定字符串

这里以nginx配置文件为例，修改日志格式。

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

改成

    log_format  main  '[$time_iso8601] - $remote_addr "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

这需要匹配log_format这行，删除[$time_local]字符串，其余做替换即可。

• 第一步：

# sed "s/\$remote_addr/[\$time_iso8601]/" 1.txt

    log_format  main  '[$time_iso8601] - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

• 第二步：

# sed -e "s/\$remote_addr/[\$time_iso8601]/" -e "s/\$remote_user/\$remote_addr/" 1.txt

    log_format  main  '[$time_iso8601] - $remote_addr [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

• 第三步：

# sed -e "s/\$remote_addr/[\$time_iso8601]/" -e "s/\$remote_user/\$remote_addr/" -e "s/\[\$time_local\] //" 1.txt

    log_format  main  '[$time_iso8601] - $remote_addr "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

另外，如果想在一行行尾增加字符串，通常是这样做：

# sed 's/$/aaa/' file1				# ^表示行首，$表示行尾

但如果将

access_log /usr/local/nginx/logs/$SERVICE_access.log;

改成

access_log /usr/local/nginx/logs/$SERVICE_access.log json;

用上面的方法是不可行的，还是需要替换字符串

# cat 2.txt
    access_log /usr/local/nginx/logs/aaaaa_access.log;
    
# SERVICE=aaaaa; sed "s/\/usr\/local\/nginx\/logs\/"$SERVICE"_access.log;/\/usr\/local\/nginx\/logs\/"$SERVICE"_access.log json;/" 2.txt
    access_log /usr/local/nginx/logs/aaaaa_access.log json;

其实不是$name要加双引号，而只是用于结束前面的双引号，和再开始后面的双引号，从而将$name置入双引号外面的shell环境中，才能得到shell解析。双引号内为sed环境。

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