Tag Archives: Bash

Unknown's avatar Namal Fernando 2:14 pm on 13th May 2020
Tags: Bash, tail   

Important tail commands

Outputs the last 10 lines of the file myfile.txt. Default is 10 lines.

tail /path/to/file/myfile.log

Outputs the last 100 lines of the file myfile.txt.

tail -n 100 /path/to/file/myfile.log

Outputs the last 10 lines of myfile.txt, and keep follow on myfile.txt for updates; Here, -f option “which stands for follow” will keep the stream going…

tail -f /path/to/file/myfile.log

Selectively keep follow a log file in real time.

tail -f /path/to/file/myfile.log | grep 24.10.160.10

Outputs the last 10 lines of myfile.txt, and keep follow on myfile.txt for updates with a sleep interval. Here, -s option is for “sleep” and specify the sleep interval

tail -f -s 5 /path/to/file/myfile.log

We can use this to in conjunction with different other commands

ps aux | sort -nk +3 | tail -5

References :

  • https://www.howtogeek.com/481766/how-to-use-the-tail-command-on-linux/

#bash, #tail

Unknown's avatar Namal Fernando 6:27 am on 12th May 2020
Tags: Bash, vi   

Important vi commands

Starting vi

  • vi filename : edit filename starting at line 1
  • vi -r filename : recover filename that was being edited when system crashed

Navigating

  • ^f : move forward one screen
  • ^b : move backward one screen
  • ^d : move down (forward) one half screen
  • ^u : move up (back) one half screen

Searching Text

  • /string : search forward for occurrence of string in text
  • ?string : search backward for occurrence of string in text
  • n : move to next occurrence of search string
  • N : move to next occurrence of search string in opposite direction

Adding / Changing / Deleting text

  • i : insert text before cursor, until hit
  • I : insert text at beginning of current line, until hit
  • a : append text after cursor, until hit
  • A : append text to end of current line, until hit
  • o : open and put text in a new line below current line, until hit
  • O : open and put text in a new line above current line, until hit

Cutting and Pasting Text

  • yy : copy (yank, cut) the current line into the buffer
  • Nyy or yNy : copy (yank, cut) the next N lines, including the current line, into the buffer
  • p : put (paste) the line(s) in the buffer into the text after the current line

Exit vi

  • : x ENTER : quit vi, writing out modified file to file named in original invocation
  • :wq ENTER : quit vi, writing out modified file to file named in original invocation
  • :q ENTER : quit (or exit) vi
  • :q! ENTER : quit vi even though latest changes have not been saved for this vi call

References :

  • https://www.cs.colostate.edu/helpdocs/vi.html

#bash, #vi

Unknown's avatar Namal Fernando 6:08 am on 12th May 2020
Tags: Bash, find, jar, search   

Finding files in side a jar

List all files in jar-file-name.jar whose name is start with “SomeFileName”

jar -tvf jar-file-name.jar | grep "SomeFileName"

List all files in a jar order by size

jar -tvf jar-file-name.jar | sort -n -r

List all the classes contains the class name with package structure.

find filePath -name '*.jar' | xargs -I @ jar -tvf @ | grep ClassName
find filePath -name '*.jar' | xargs -I @ jar -tvf @ | grep /ClassName

Search and print the jar names and if the class exists then print the class name.

find filePath -name '*.jar' | while read F; do (echo $F; jar -tvf $F | grep ClassName.class) done

Search and print the jar name if the class exsists then prints the class name. (exact match only)

find filePath -name '*.jar' | while read F; do (echo $F; jar -tvf $F | grep /ClassName.class) done

#bash, #find, #jar, #search