A Technical I.T./DevOps Blog
Problem scenario
You want to substitute the nth word of a given line. How do you use awk to accomplish this?
Solution
Let’s assume the lines that you want to modify are in goodfile.txt. To replace the fourth item in the string with “new string”, run this command:
cat goodfile.txt | awk ‘{ print $1 ” ” $2 ” ” $3 ” new string ” $5 ” ” $6 }’
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Problem scenario
You want to run a Java program via a .jar file. You want to invoke it like this java -jar nameOf.jar
What do you do?
Solution
1. Install Maven. If you need assistance, see this posting.
2. Follow these directions.
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Continue reading “How Do You Create a .jar File for Your Java Program?”
You have one of the following two problems:
Problem scenario #1
Your GCP startup-script is not working. You do not know why. What should you do?
OR
Problem scenario #2
A bash script is not working. It stops executing after a certain line. There are few clues as to what is wrong.
Solution
Did you copy the script from a webpage?
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Continue reading “How Do You Troubleshoot a Bash Script Copied from the Internet?”
Question
Why did Apple call one of their computers the Macintosh?
Answer
It was based on a type of apple that you eat (e.g., golden delicious, Fuji, etc.). It would have been called the McIntosh, but there were legal reasons for adding the letter “a”. To read more about how the name was chosen, see this page.
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Continue reading “Why Did Apple Call One of Their Computers Macintosh?”
Problem scenario
You want to delete all the files (but not subdirectories) that are less than 10 KB in Linux’s /tmp/ directory. How do you do this?
Solution
Run this command: find /tmp/ -maxdepth 1 -type f -size -10k -ls | awk ‘{print $NF}’ | rm -rf
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Problem scenario
When you press the up arrow on the keyboard you see ” ^[[A”. You want to see the previous command that was entered. How do you enable history at the command line?
Solution
Root cause: The /etc/passwd file has an entry like this:
cooluser:x:1001:1002::/home/cooluser:
(This could be caused if you created the user quickly with a useradd command.)
Procedures
Run this command: sudo cat /etc/passwd | grep $(whoami)
Do you see a /bin/bash at the end?
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Continue reading “How Do You Get the “Up” Arrow to Show a Previous Command in Linux?”
Problem scenario
You backed up /var/log/mail to a different file. You want the /var/log/mail file to start empty so you can review it without looking at old activity. What do you do?
Solution
Run these four commands:
sudo su –
cd /var/log
mail
exit
Now you /var/log/mail file will still exist and record activity as normal. It will not have anything in it before the time you ran the above “>
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Continue reading “How Do You Zero out a /var/log/mail File?”
Problem scenario
In Linux you want to delete files that have not been modified in the past three days from the /tmp/ directory. What do you do?
Solution
Run this: find /tmp/ -maxdepth 1 -type f -atime -3 -ls | awk ‘{print $NF}’ | rm -rf
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Continue reading “How Do You Delete Files That Were Modified More Than Three Days Ago?”
Problem scenario
You see two underscores or two underbars before a function in Python. What does this syntax signify?
Possible Solution #1
The answer is best explained by running this program once with no modification and a second time with a modification.
class ContintClass():
def __init__(self):
self.__completelyprivate = “1111111111”
self._semiprivate = “2222222”
foo = ContintClass()
#print(foo.__completelyprivate)
print(“Above is an attempt to print a completely private data member of an object”)
print(“Below is an attempt to print a semi-private data member of an object”)
print(foo._semiprivate)
Before you run the program the second time,
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Problem scenario
The elasticsearch, logstash or kibana services will start, but when you check the status, it does not remain on. It keeps stopping. You see the status as “failed.”
Solution
Possible Solution #1
Add more memory or swap space to the system. If you need assistance with either of these, see this posting.
Possible Solution #2
Go to the logs directory for elasticsearch.
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Continue reading “How Do You Get the ElasticSearch, LogStash or Kibana Service to Remain On?”