Home / Questions / 224501
Accepted
ortiga
Asked: 2020-12-20 10:21:01 +0800 CST 2020-12-20 10:21:01 +0800 CST

Comment a line in a .log file

  • 772

Hi, I have the following code:

 !/bin/bash

  while read line;
  do

  echo "$line";
   if[???????]
   fi

  done < /home/javi.log

javi.log file:

#

javi_2223
javi55_555
imp33
imp44
javi32423
javi5646

I want the script to comment the lines imp33 and imp44 I know what would be done with if but I don't know what to use to comment them...

It would be as follows:

#

javi_2223
javi55_555
#imp33
#imp44
javi32423
javi5646

if the file were like this: how would it be putting the :space it does not take it for me

javi_2223
javi55_555

#imp33
#imp44

javi32423
javi5646
bash

1 Answers

  1. Best Answer

    Wearingbash

    To get the best result bashand to make it easier to add new terms, I recommend you use caseinstead of ifnested ones as follows:

    #!/bin/bash

# read limpia espacios por delante y por detrás del texto
while read line
do
  # Dependiendo del contenido de $line ...
  case "$line" in
    imp33|imp44)
      # Si es "imp33" o "imp44" agregamos un # delante
      echo "#${line]"
      ;;
    *)
      # En caso contrario mostramos tal cual la línea
      echo "$line";
      ;;
  esac
done < /home/javi.log

    Wearingsed

    The most efficient way to do what you want is to use the tool sedusing the following substitution pattern:

    sed -r 's/^(imp33|imp44)$/#\1/' /home/javi.log

    Of all the functionality it offers, sedI have used the "substitution" function ( sfrom substitute ) which has the following format: s/patrón/sustitución/opciones. In my case I haven't used any option, but you could use i, for example, to make the search case insensitive.

    In the online version you will see a description of how the pattern and capture groups work:

    • Start of line ^.
    • Capture Group ():
      • option imp33.
      • option imp44.
    • End of line $.

    Whatever is on the line, if the capture pattern is met, will be replaced by #\1what it means:

    • A hash symbol #.
    • Content of the first capturing group \1.

    Unlike the version in bash, blank characters before and after the text are not removed, so if you want the behavior to be the same you should use the following pattern:

    sed -r 's/^[[:space:]]*(imp33|imp44)[[:space:]]*$/#\1/' /home/javi.log

    In the online version you will see a description of how the pattern and capture groups work:

    • Start of line ^.
    • 0 or more space characters, tabs, etc ( [ \t\r\n\v\f]).
    • Capture Group ():
      • option imp33.
      • option imp44.
    • 0 or more space characters, tabs, etc ( [ \t\r\n\v\f]).
    • End of line $.

    As the blank characters have not been included in the capturing group they will not be in the substitution, which will remain the hash character #followed by the capturing group.

    You can learn more about how it works sed(thanks to @Juan and @JackNavaRow for the suggestion) on the following pages:

    • 12