Find only the matched pattern in a CSV file

Question

I am trying to print only the matched pattern in a CSV file. Example: all the columns value starting with 35=its value. Thanks.

CSV file:

35=A,D=35,C=129,ff=136
D=35,35=BCD,C=129,ff=136
900035=G,D=35,C=129,ff=136
35=EF,D=35,C=129,ff=136,35=G
36=o,D=35,k=1

Output:

35=A
35=BCD
35=EF
35=G

The command I used did not work:

sed -n '/35=[A-Z]*?/ s/.*\(35=[A-Z]*?\).*/\1/p' filename

Answer 1

Using tr to replace all commas with newlines, and then grep to get all lines that start with the string 35=:

$  tr ',' '\n' <data.in | grep '^35='
35=A
35=BCD
35=EF
35=G

Answer 2

With GNU grep which supports -o option to print only matched string, each on its own line

$ grep -oE '\b35=[^,]+' ip.csv 
35=A
35=BCD
35=EF
35=G

• \b is word boundary, so that 900035 won't match
• [^,]+ to match one or more non, characters
• assumes the values do not contain ,

With awk

$ awk -F, '{ for(i=1;i<=NF;i++){if($i~/^35=/) print $i} }' ip.csv 
35=A
35=BCD
35=EF
35=G

• -F, set , as input field separator
• for(i=1;i<=NF;i++) iterate over all fields
• if($i~/^35=/) if field starts with 35=
  • print $i print that field

Similar with perl

perl -F, -lane 'foreach (@F){print if /^35=/}' ip.csv 

Answer 3

With perl:

$ perl -lne 'print for /(\b35=[^,]+)/g' filename
35=A
35=BCD
35=EF
35=G

or perhaps more generally/robustly using the Text::CSV module

$ perl -MText::CSV -lne '
  BEGIN{$p = Text::CSV->new()} 
  print for grep { /^35=/ } $p->fields(), $p->parse($_)
' filename
35=A
35=BCD
35=EF
35=G

Answer 4

Perl lookarounds with grep work really well.

grep -oP '(?<=35\=).*?(?=,)'

This returns the exact information minus the 35= bit

grep -oP '(?<=35\=).*?(?=,)' file.csv will return this

A
BCD
G
EF

Answer 5

Pure Bash solution:

(                                                  # Use parentheses as scope for IFS
    IFS=$',\n'                                     # Split on both , or \n
    for c in $(</tmp/file.csv)                     # For every column or row
    do
        [[ "$c" =~ ^35= ]] && echo ${line##35=}    # Find ^35= and print while removing ^35=
    done
) # Optionally >/tmp/filtered-output.txt

Note, only use this for its readability and flexibility - if you can read it, otherwise you can use the following approach:

# Read            | Replace     | Find        | Remove
cat /tmp/file.csv | tr ',' '\n' | grep '^35=' | sed 's/^35=//'

which is more intuitive and efficient.

Input (/tmp/file.csv):

35=A,D=35,C=129,ff=136
D=35,35=BCD,C=129,ff=136
900035=G,D=35,C=129,ff=136
35=EF,D=35,C=129,ff=136,35=G
36=o,D=35,k=1

Output:

A
BCD
EF
G