Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. It only takes a minute to sign up.
Sign up to join this community
I'm working in HDFS and am trying to get the entire line where the 4th column starts with the number 5:
100|20151010|K|5001
695|20151010|K|1010
309|20151010|R|5005
410|20151010|K|5001
107|20151010|K|1062
652|20151010|K|5001
Hence should output:
100|20151010|K|5001
309|20151010|R|5005
410|20151010|K|5001
652|20151010|K|5001
The simplest approach would probably be awk:
awk -F'|' '$4~/^5/' file
The -F'|' sets the field separator to |. The $4~/^5/ will be true if the 4th field starts with 5. The default action for awk when something evaluates to true is to print the current line, so the script above will print what you want.
Other choices are:
Perl
perl -F'\|' -ane 'print if $F[3]=~/^5/' file
Same idea. The -a switch causes perl to split its input fields on the value given by -F into the array @F. We then print if the 4th element (field) of the array (arrays start counting at 0) starts with a 5.
grep
grep -E '^([^|]*\|){3}5' file
The regex will match a string of non-| followed by a | 3 times, and then a 5.
GNU or BSD sed
sed -En '/([^|]*\|){3}5/p' file
The -E turns on extended regular expressions and the -n suppresses normal output. The regex is the same as the grep above and the p at the end makes sed print only lines matching the regex.
-E isn't mentioned in either man or info. It does activate ERE, right?
-Extended regexp is slated for the next POSIX version, too, so might as well just get used to it. plus, -r doesn't make any sense. and yeah, it's a synonym - they both do exactly the same thing. almost the same - i think w/ -r you can switch back -re ... -Ge ... or something, but who would?
This will print all lines that match |5 and then no more | until the end of the line:
grep '|5[^|]*$' <in >out
If you want answers using tools that are CSV-aware to account for CSV files containing fields with embedded | characters and newlines, then here's how you do it with mlr (Miller):
mlr --csv --fs '|' -N filter -S '${4} =~ "^5"' file
This makes mlr read the original data as a header-less CSV file using | as the field separator (this is what --csv --fs '|' -N does). It applies a filter expression that extracts the records for which the expression is true. While doing so, it avoids inferring data types and treats the data as strings (-S, because regular expressions are generally only applicable to strings).
The expression matches the regular expression ^5 to the fourth field of the record.
Extracted records are reproduced as CSV with the same field separator as the input.
You can do the same sort of thing with the tools from the csvkit package, but since there's no way to tell csvgrep to use a custom field separator for the output, you will have to reformat the result with csvformat if you want to retain your | separators:
csvgrep -d '|' -H -c 4 -r '^5' file | csvformat -K 1 -D '|'
The -K 1 options to csvformat skips the anonymous header line produced by csvgrep.
Using Raku (formerly known as Perl_6)
~$ raku -ne '.put if .split("|")[3].starts-with("5");' file
Sample Input:
100|20151010|K|5001
695|20151010|K|1010
309|20151010|R|5005
410|20151010|K|5001
107|20151010|K|1062
652|20151010|K|5001
Sample Output:
100|20151010|K|5001
309|20151010|R|5005
410|20151010|K|5001
652|20151010|K|5001
Briefly, Raku is directed to read input linewise off the command line using the -ne flags (n means non-autoprinting). Lines are output if, when split on | vertical-bar, the zero-indexed 3-rd element (i.e. fourth column) starts-with("5").
For more complicated CSV files, use Raku's Text::CSV module.
https://unix.stackexchange.com/a/705099/227738
https://raku.org
