SED: insert something after the second last line?

sed

12,186

Solution 1

To insert a line before the last ($) one:

$ cat test
one
two
three
four
five

$ sed '$i<hello>!' test
one
two
three
four
<hello>!
five

That's for GNU sed (and beware leading spaces or tabs are stripped). Portably (or with GNU sed, if you want to preserve the leading spaces or tabs in the inserted line), you'd need:

sed '$i\
<hello>!' test

Solution 2

Yes, sed can be told to act on only a specific line by writing the line number before the operation you tell it to perform. For example, to insert a line with the string foo after the 4th line of a file, you could do:

sed '4s/$/\nfoo/' file  # GNU sed and a few others
sed '4s/$/\
foo/' file # standardly/portably

To insert a line after the next to last line, I can think of two approaches:

Count the number of lines first and then make the edit:
```
sed "$(( $( wc -l < file) -2 ))s/$/\nfoo/" file
```
Use tac:
```
tac file | sed '2s/$/\nfoo/' | tac
```

12,186

Fractaliste

French IT engineer. Prefered language : Java Prefered framework : Laravel Prefered solver : Choco Prefered metasyntactic variable : plop Prefered quote : There are 10 kind of people on the world, those who understand binary, and those who don't. If needed, you can contact me on : fractaliste at gmail dot com

Updated on September 18, 2022

Comments

Fractaliste over 1 year

In a XML configuration file I need to add a line, in order to not to break the last closing tag. Is it possible to do it with SED ?

The number of line of the whole file can change from a server to another...

Edit : Some exemple of file I need to edit :

<configuration>

  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <!-- encoders are assigned the type
         ch.qos.logback.classic.encoder.PatternLayoutEncoder by default -->
    <encoder>
      <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
    </encoder>
  </appender>

  <root level="debug">
    <appender-ref ref="STDOUT" />
  </root>
</configuration>

An other exemple:

  <?xml version="1.0" encoding="UTF-8"?>
  <configuration>

    <property name="DEV_HOME" value="c:/logs" />

    <appender name="FILE-AUDIT"
      class="ch.qos.logback.core.rolling.RollingFileAppender">
      <file>${DEV_HOME}/debug.log</file>
      <encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
        <Pattern>
          %d{yyyy-MM-dd HH:mm:ss} - %msg%n
        </Pattern>
      </encoder>

      <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
        <!-- rollover daily -->
        <fileNamePattern>${DEV_HOME}/archived/debug.%d{yyyy-MM-dd}.%i.log
                          </fileNamePattern>
        <timeBasedFileNamingAndTriggeringPolicy
          class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
          <maxFileSize>10MB</maxFileSize>
        </timeBasedFileNamingAndTriggeringPolicy>
      </rollingPolicy>

    </appender>

    <logger name="com.mkyong.web" level="debug"
      additivity="false">
      <appender-ref ref="FILE-AUDIT" />
    </logger>

    <root level="error">
      <appender-ref ref="FILE-AUDIT" />
    </root>

    <logger name="com.mkyong.ext" level="debug"
      additivity="false">
      <appender-ref ref="FILE-AUDIT" />
    </logger>

      <logger name="com.mkyong.other" level="info"
      additivity="false">
      <appender-ref ref="FILE-AUDIT" />
    </logger>

      <logger name="com.mkyong.commons" level="debug"
      additivity="false">
      <appender-ref ref="FILE-AUDIT" />
    </logger>
  </configuration>

Fractaliste about 7 years

@StephenKitt You're right but I need tools included with Ubuntu12 because I can't install new tools on the server.
don_crissti about 7 years

What a mess... Could you perhaps post a very short input sample and the expected output ?
Kusalananda about 7 years

Why can't you install tools on the server?
Fractaliste about 7 years

@Kusalananda it's a secured environment and each tools to be installed have to be tested and validated by a dedicated team. It's more a corporate's process problen than an inability to install it.
Stephen Kitt about 7 years

And yet you’re allowed to manipulate Log4J XML files directly on the server? O_O
Kusalananda about 7 years

Notice that any script that comes out of here may be considered a tool that needs to be tested and validated too. Just saying.

Fractaliste about 7 years

As far as I understand I can't use the sed's -i option with tac?
terdon about 7 years

@Fractaliste no, not with tac, but you can always do tac file | sed '2s/$/\nfoo/' | tac > newfile && mv newfile file
Stéphane Chazelas about 7 years

You just sed '$s/^/foo\n/' to insert before the last one.
terdon about 7 years

@StéphaneChazelas yes, I know that now, after reading Kamaraj's answer, but I wasn't aware of that when I posted mine.
ACK_stoverflow about 2 years

For anyone who, like me, is trying to insert a leading tab with this solution and running into problems (perhaps because I'm using sed from busybox?) the following works: sed -e '$i \' -e $'\t'"scan_ssid=1" /tmp/connect.conf