print nth, (n+3)rd, ((n+3)+3)rd,.... lines using awk

Question

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ADD file ... in /
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CMD ["bash"]
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ENV DEBIAN_FRONTEND=noninteractive
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COPY file:6229791a987783682b536a308b0d287c470ec1bfa0be9b6b3471feab66706874 in /install.sh
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/bin/sh -c /install.sh && rm
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ARG SPLUNK_FILENAME
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ARG SPLUNK_BUILD_URL
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ARG SPLUNK_DEFAULTS_URL
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ENV SPLUNK_HOME=/opt/splunkforwarder SPLUNK_GROUP=splunk SPLUNK_USER=splunk
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|1 SPLUNK_BUILD_URL=http://releases.splunk.com/dl/orangeswirl_builds/7.2.1-20181119-0400/splunkforwarder-7.2.1-be11b2c46e23-Linux-x86_64.tgz /bin/sh -c groupadd
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USER splunk
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COPY dir:6e993b24f9f98057163ef8bd8c62e4861acd5bfa0b2053e0e38f2945df2a8e2a in /opt/ansible
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COPY multi:96216845d7aa8a7c7fe1625c00b24c9cf8c2077b7bfb6cd2170777135f01fa20 in /sbin/
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COPY multi:fb03ac2df458b42167388f14efe28124d79c80127da9acdba91b01e5ef99d67d in /tmp/
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EXPOSE 8088 8089 9997
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VOLUME [/opt/splunkforwarder/etc /opt/splunkforwarder/var]
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HEALTHCHECK &{["CMD-SHELL" "/sbin/checkstate.sh ||
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ENTRYPOINT ["/sbin/entrypoint.sh"]
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CMD ["start-service"]
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Command

I have copied the dockerfile contentfrom dockerhub but it comes with line number and sizes, I want to create an awk control file to extract just the dockerfile content without the numbers or sizes. That is, I want to print 2nd,5th,8th,11th and so on lines. I can do it with bash scripting but I'm learning awk and want to do it that way.

Edit:

ADD file ... in /
CMD ["bash"]
ENV DEBIAN_FRONTEND=noninteractive
COPY file:6229791a987783682b536a308b0d287c470ec1bfa0be9b6b3471feab66706874 in /install.sh
/bin/sh -c /install.sh && rm
ARG SPLUNK_FILENAME
ARG SPLUNK_BUILD_URL
ARG SPLUNK_DEFAULTS_URL
ENV SPLUNK_HOME=/opt/splunkforwarder SPLUNK_GROUP=splunk SPLUNK_USER=splunk
|1 SPLUNK_BUILD_URL=http://releases.splunk.com/dl/orangeswirl_builds/7.2.1-20181119-0400/splunkforwarder-7.2.1-be11b2c46e23-Linux-x86_64.tgz /bin/sh -c groupadd
USER splunk
COPY dir:6e993b24f9f98057163ef8bd8c62e4861acd5bfa0b2053e0e38f2945df2a8e2a in /opt/ansible
COPY multi:96216845d7aa8a7c7fe1625c00b24c9cf8c2077b7bfb6cd2170777135f01fa20 in /sbin/
COPY multi:fb03ac2df458b42167388f14efe28124d79c80127da9acdba91b01e5ef99d67d in /tmp/
EXPOSE 8088 8089 9997
VOLUME [/opt/splunkforwarder/etc /opt/splunkforwarder/var]
HEALTHCHECK &{["CMD-SHELL" "/sbin/checkstate.sh ||
ENTRYPOINT ["/sbin/entrypoint.sh"]
CMD ["start-service"]
Command

this should be the final output.

I'm at

awk 'BEGIN{NR==2 print $0}{NR==5,NR==8,... print $0}'

I'm not sure if we can sort in BEGIN block and how to use increment logic with NR varaible.

Could you please do your efforts in form of code in your question along with sample expected output in your question and let us know then. — RavinderSingh13, Jun 14 '20 at 05:44
hint: use modulus operator and special variable that has line number — Sundeep, Jun 14 '20 at 05:45
here's another hint: https://stackoverflow.com/questions/9968916/print-every-nth-line-into-a-row-using-gawk — Sundeep, Jun 14 '20 at 05:47
@Sundeep Yes, I know NR is the variable and every nth line is easier and not quite I'm looking for. — Kosmos Nagios, Jun 14 '20 at 05:53
See Sundeep's [hint](https://stackoverflow.com/questions/62368803/print-nth-n3rd-n33rd-lines-using-awk?noredirect=1#comment110304442_62368803).. Start with second row and output every third row: `awk 'NR%3==2' file` — Cyrus, Jun 14 '20 at 05:56
@Cyrus perfect, Can you add it to answers, so I can accept the answer. — Kosmos Nagios, Jun 14 '20 at 05:58
@KosmosNagios: I closed your question with a link to a very similar question — Cyrus, Jun 14 '20 at 05:59

print nth, (n+3)rd, ((n+3)+3)rd,.... lines using awk

0 Answers0