Bash Script Regular Expressions…How to find and replace all matches?

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终归单人心
终归单人心 2021-01-17 14:40

I am writing a bash script that reads a file line by line.

The file is a .csv file which contains many dates in the format DD/MM/YYYY but I would like to change the

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  • 2021-01-17 14:53

    I don't wanna echo...I want to store the result in a new variable

    to do that (and i know this isn't exacting to your setup, but still applies in how to use a regex):

    path="/entertainment/Pictures"
    files=(
      "$path"/*.jpg"
      "$path"/*.bmp"
    )
    
    for i in "${files[@]}"
    do
      # replace jpg and bmp with png in prep for conversion
      new=$(echo "$i" | perl -pe "s/\.jpg|\.bmp/.png")
    
      # next is to perform the conversion
      ...
    done
    
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  • 2021-01-17 15:03

    Try this using sed:

    line='Today is 10/12/2010 and yesterday was 9/11/2010'
    echo "$line" | sed -r 's#([0-9]{1,2})/([0-9]{1,2})/([0-9]{4})#\3-\2-\1#g'
    
    OUTPUT:
    Today is 2010-12-10 and yesterday was 2010-11-9
    

    PS: On mac use sed -E instead of sed -r

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  • 2021-01-17 15:03

    Pure Bash.

    infile='data.csv'
    
    while read line ; do
      if [[ $line =~ ^(.*),([0-9]{1,2})/([0-9]{1,2})/([0-9]{4}),(.*)$ ]] ; then
        echo "${BASH_REMATCH[1]},${BASH_REMATCH[4]}-${BASH_REMATCH[3]}-${BASH_REMATCH[2]},${BASH_REMATCH[5]}"
      else
        echo "$line"
      fi
    done < "$infile"
    

    The input file

    xxxxxxxxx,11/03/2011,yyyyyyyyyyyyy          
    xxxxxxxxx,10/04/2011,yyyyyyyyyyyyy          
    xxxxxxxxx,10/05/2012,yyyyyyyyyyyyy          
    xxxxxxxxx,10/06/2011,yyyyyyyyyyyyy          
    

    gives the following output:

    xxxxxxxxx,2011-03-11,yyyyyyyyyyyyy
    xxxxxxxxx,2011-04-10,yyyyyyyyyyyyy
    xxxxxxxxx,2012-05-10,yyyyyyyyyyyyy
    xxxxxxxxx,2011-06-10,yyyyyyyyyyyyy
    
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  • 2021-01-17 15:14

    You can do it using sed

    echo "11/12/2011" | sed -E 's/([0-9][0-9]?)\/([0-9][0-9]?)\/([0-9][0-9][0-9][0-9])/\3-\2-\1/'
    
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