Shiva's Weblog

 Unix related

 $ ls -l ## show list of files and directories.   

total 447

drwxrwxrwx 5 schalla        challanet  2017 Dec 12 07:44 dir1

-rw-r--r-- 1 schalla challanet 94056 Dec 12 09:33 file1.csv

-rw-r--r-- 1 schalla challanet 37880 Dec 11 14:38 file2.csv

drwxr-xr-x 2 schalla challanet    36 Dec 12 05:34 dir2


 $ ls -ltr ## l = show List, t = Sort by Time, r = in reverse order (ascending order)
 $ ls -lsr ## l = show List, s = Sort by size, r = in reverse order (ascending order)

AWK:


Read data line by line and act upon the strings and patterns in each of those lines.
$ ls -l | awk '{print $9}'


dir1

file1.csv

file2.csv

dir2

$ echo "str1,str2,str3" | awk -F',' '{print $2}'
str2

$ printf "str1\tstr2\tstr3" |awk -F'\t' '{print $2}'  
str2

SED:


SED stands for Stream EDitor


$ echo "it is sunny out" |sed s/sunny/rainy/
$ echo "it is sunny out" |sed s#sunny#rainy#
$ echo "it is sunny out" |sed s@sunny@rainy@
$ echo "it is sunny out" |sed s:sunny:rainy:
$ echo "it is sunny out" |sed s_sunny_rainy_

it is rainy out


** all the above commands will produce the same result 

s           substitute command

/,#,@,:,_   Delimiter(s); there are more. 

sunny     Search string; could use Regex pattern.

rainy      Replacement string

&           Replaces the original string  (see below)




$ echo "it is sunny out" |sed 's:sunny:"&":'<
it is "sunny" out

$ echo "it is sunny out" |sed 's:sunny:(&):'
it is (sunny) out

$ echo "it is sunny out" |sed 's:sunny:"&-&":'
it is "sunny-sunny" out

$ echo "it is sunny out" |sed 's:sunny:"&-&-&":'
it is "sunny-sunny-sunny" out

 
GREP: 
 
Stands for: Global regular expression print
 
Function: Search for PATTERN in each FILE or standard input
 
 (note: grep is case sensitive - this is inline with everything *nix. All *nix based shells are usually case-sensitive)
 

  $grep ERROR {filename}  ##This will print lines that has the word "ERROR" 
  $ls -ltr |grep '.sql$' ##this will print lines that end with ".sql". The "$" symbol indicates that the preceeding character is the last character.
 $ $ ls -l | grep '^d'  ##this will print lines that start with the letter "d". The "^" symbol indicates that the following is the first character'
 
drwxrwxrwx 5 schalla        challanet  2017 Dec 12 07:44 dir1
 
drwxr-xr-x 2 schalla challanet    36 Dec 12 05:34 dir2
 $ ls -l | grep -v '^d' *[2]
 
-rw-r--r-- 1 schalla challanet 37880 Dec 11 14:38 file2.csv
 

  $grep ERROR -A 20 -B 30 {filename}  
 ##This will print lines that has the word "ERROR" 
 
 additionally, it will display 20 lines preceeding (-A 20) the hit-line and 30 lines succeeding the hit-line (-B 30).

Removing Blank lines in a file:

grep . FILENAME

sed -e /^$/d FILENAME

awk /./ FILENAME

file ##shows character encoding details

$ file -i {{filename.ext}} 
 
filename.ext: text/xml; charset=iso-8859-1
 

    
od }} print file/stdin as Octal Bytes  

    $ od -c filename.ext 
 
    -c option will show ASCII printable characters & backslash escapes.

VIM

/ searches the text prefixed with / command

/hello # searches for hello in the open file

:substitute command
it finds a text patten and replaces it based on one of the options 

:%s/searchterm/replaceterm/g

    Find & replace in all lines 

:%s/searchterm/replaceterm/gc

    does same a above but with confirmation for each replacement.

:s/searchterm/replaceterm/g

    Find & replace in current line only; notice the absense of %, making this only applicable to one line

:s/searchterm/replaceterm/gi

    same as above but with case insensitive

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