UNIX Interview Questions | ETL

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UNIX Commands for ETL Developer/ Tester/ Support

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• LIST 

1) Unix command to list files in descending order

ls -ltr

2) Unix command to list files based on file size

ls -ls

3) Unix command to list hidden files 

ls -la | grep ^[.]

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• KILL

1) UNIX command to kill background jobs

KILL $!

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• PRINT

1) UNIX command to print the first line of the  file

HEAD -1 filename.txt
or 
SED '2$' filename.txt

2) UNIX command to print the last line of the  file

TAIL -1 filename.txt
or 
SED -n '$p' filename.txt

3) UNIX command to print an Nth line of the  file

SED -n '<n> $p' filename.txt

<n> - number of line

4) UNIX command to print a word in reverse

echo 
| rev

5) UNIX command print the last word of a line

echo 'C for Car' | rev | CUT -f 1 d ' ' | rev

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• REMOVE

1) UNIX command to remove the first line of the file 

SED '1d' filename.txt

2) UNIX command to remove the last  line of the file 

SED  -i '$d' filename.txt

3) UNIX command to remove Nth line of the  file

SED  -i '<n> $d' filename.txt

<n> - number of line

4) UNIX command to remove the empty line from the file 

GREP -v ^"$" filename.txt

5) UNIX command to cut Nth word of a line

 

CUT -f <n> -d ' '

<n> - number of line

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• COUNT 

1) UNIX command to find the number of lines in the file

filename.txt | wc -l

2) UNIX command to find the length of the Nth line in the file

SED -n '<n> p' filename.txt | wc -L

<n> - number of line

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• OTHERS

1) View non-printable words in the file

vi filename.txt 

In vi mode you can view the non-printable words in the file

2) Remove BOM characters

SED -i '1s/^\xEF\xBB\xBF//' filename.txt

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