This is similar to PHP's array_diff and Java's removeAll(). Helpful in finding diffs between lists of ids.

angelcool@fedora-laptop$cat FILE1.txt 
1
2
3
4
5
5
angelcool@fedora-laptop$cat FILE2.txt 
1
2
3
4
5
6
7
8
9
angelcool@fedora-laptop$comm -13 <(sort FILE1.txt|uniq) <(sort FILE2.txt|uniq)
6
7
8
9
angelcool@fedora-laptop$ man comm
...
       Compare sorted files FILE1 and FILE2 line by line.

       When FILE1 or FILE2 (not both) is -, read standard input.

       With  no  options,  produce three-column output.  Column one contains lines unique to FILE1, column two con‐
       tains lines unique to FILE2, and column three contains lines common to both files.

       -1     suppress column 1 (lines unique to FILE1)

       -2     suppress column 2 (lines unique to FILE2)

       -3     suppress column 3 (lines that appear in both files)

       --check-order
              check that the input is correctly sorted, even if all input lines are pairable

       --nocheck-order
              do not check that the input is correctly sorted

       --output-delimiter=STR
              separate columns with STR

       --total
              output a summary

       -z, --zero-terminated
              line delimiter is NUL, not newline

       --help display this help and exit

       --version
              output version information and exit

       Note, comparisons honor the rules specified by 'LC_COLLATE'.
...

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---

[acool@acool2 ~]$ sudo yum install at
...
[acool@acool2 ~]$ sudo systemctl start atd
[acool@acool2 ~]$ sudo systemctl enable atd


[acool@acool2 ~]$ date
Mon Apr 15 16:09:15 PDT 2019
[acool@acool2 ~]$ 
[acool@acool2 ~]$ echo 'date >> at-fun.txt'  | at now + 1 minute
job 79 at Mon Apr 15 16:10:00 2019
[acool@acool2 ~]$ 
[acool@acool2 ~]$ atq
79	Mon Apr 15 16:10:00 2019 a acool
[acool@acool2 ~]$ 
[acool@acool2 ~]$ cat at-fun.txt 
Mon Apr 15 16:10:00 PDT 2019


[acool@acool2 ~]$ 
[acool@acool2 ~]$ cat at-fun.txt 
[acool@acool2 ~]$ echo 'php -v >> at-fun.txt'  | at 4:16 PM April 15 2019
job 84 at Mon Apr 15 16:16:00 2019
[acool@acool2 ~]$ 
[acool@acool2 ~]$ date
Mon Apr 15 16:15:21 PDT 2019
[acool@acool2 ~]$ atq
84	Mon Apr 15 16:16:00 2019 a acool
[acool@acool2 ~]$ 
[acool@acool2 ~]$ cat at-fun.txt 
PHP 7.0.27 (cli) (built: Apr  4 2018 13:48:44) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2017 Zend Technologies
[acool@acool2 ~]$ 

https://stackoverflow.com/questions/55524769

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---

Cool way to make sure a key does not exist in a group of memcached servers. Handy when troubleshooting or when cached data needs a purge. Tested:

[aesteban@localhost ~]$ 
[aesteban@localhost ~]$ for i in {1..6};do ( echo 'delete events.slick-range') | nc  server-${i}.example.com 11211; done;
NOT_FOUND
NOT_FOUND
NOT_FOUND
DELETED
NOT_FOUND
NOT_FOUND
[aesteban@localhost ~]$ 
[aesteban@localhost ~]$ 
[aesteban@localhost ~]$ 

Try adding a delay if the above doesn't seem to work:

[aesteban@localhost ~]$ 
[aesteban@localhost ~]$ for i in {1..6};do ( sleep 2; echo 'delete events.slick-range') | nc -d 2  server-${i}.example.com 11211; done;
NOT_FOUND
NOT_FOUND
NOT_FOUND
DELETED
NOT_FOUND
NOT_FOUND
[aesteban@localhost ~]$ 
[aesteban@localhost ~]$ 
[aesteban@localhost ~]$ 

BONUS (6/12/2019) - Find out the expiration date for a key:

(sleep 1; echo "stats cachedump 7 0"; sleep 1; echo "quit";) | nc www-server01.example.com  11211 | grep 'memc.sess.tpnm0jd8aottlturb0ml510sd0'

Increase/decrease the slab (seven) number as need until the key is found.

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---

Content of getThem.sh :

cd logos;

while read line; do

   # test if line starts with "assets"
   if [[ $line =~ ^asset.* ]]; then
     #prepend domain
     line="http://www.soy-example.com/$line"
   fi
  
   # test if line starts with "/assets"
   if [[ $line =~ ^/asset.* ]]; then
     # prepend domain
     line="http://www.soy-example.com$line"
   fi
  
   # download this sucker
   wget $line

done < ../soyFranquiciasLogos.txt

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---

positional parameters, parameters passed to script.

$1, $2, $3, ... 

It's an array-like construct of all positional parameters, {$1, $2, $3 ...}.

"$@" 

It's the IFS expansion of all positional parameters, $1 $2 $3 ....

"$*" 

It's the number of positional parameters.

$# 

current options set for the shell.

$- 

pid of the current shell (not subshell).

$$ 

most recent parameter (or the abs path of the command to start the current shell immediately after startup).

$_ 

It's the (input) field separator.

$IFS 

It's the most recent foreground pipeline exit status.

$? 

It's the PID of the most recent background command.

$!

It's the name of the shell or shell script.

$0

http://stackoverflow.com/questions/5163 ... -variables

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---

EXAMPLE A) Declaring a function in sum.sh script:

#!/usr/bin/bash

sum()
{
   echo $1 + $2 | bc
}

# call function and pass cli
# parameters to function
sum $1 $2

Calling script:

[aesteban@localhost ~]$ ./sum.sh 1.4 1.3
2.7

EXAMPLE B) A different way to write sum.sh script:

#!/usr/bin/bash

sum()
{
   RESULT=$(echo $1+$2 | bc) # or: RESULT=`echo $1+$2 | bc`
}

sum $1 $2

echo $RESULT

Calling modified script:

[aesteban@localhost ~]$ ./sum.sh 1.7 1.2
2.9

EXAMPLE C) Another way to write the same crap:

#!/usr/bin/bash

sum()
{
   echo $1+$2 | bc
}

SUMRESULT=`sum $1 $2`

echo $SUMRESULT

Calling it:

[aesteban@localhost ~]$ ./sum.sh 2.9 3
5.9

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---

#local variables
[aesteban@localhost ~]$ Name=Angel
[aesteban@localhost ~]$ echo $Name
Angel
[aesteban@localhost ~]$ Name="Angel Cool"
[aesteban@localhost ~]$ echo $Name
Angel Cool
[aesteban@localhost ~]$ #readonly
[aesteban@localhost ~]$ readonly Name
[aesteban@localhost ~]$ Name="Angel Esteban"
bash: Name: readonly variable
[aesteban@localhost ~]$

#index arrays
[aesteban@localhost ~]$ Fruits[0]=apple
[aesteban@localhost ~]$ Fruits[1]=orange
[aesteban@localhost ~]$ Fruits[2]=banana
[aesteban@localhost ~]$ Fruits[3]=grapes
[aesteban@localhost ~]$ 
[aesteban@localhost ~]$ States=("California" "Texas" "Florida")
[aesteban@localhost ~]$ echo ${States[1]}
Texas

[aesteban@localhost ~]$ echo ${Fruits[2]}
banana
[aesteban@localhost ~]$ echo ${Fruits[*]}
apple orange banana grapes
[aesteban@localhost ~]$ echo ${#Fruits[*]}
4
[aesteban@localhost ~]$ unset Fruits
[aesteban@localhost ~]$ echo ${!States[*]}
0 1 2
[aesteban@localhost ~]$

#associative arrays
[aesteban@localhost ~]$ declare -A INFO
[aesteban@localhost ~]$ 
[aesteban@localhost ~]$ INFO["name"]="Angel Esteban Cool"
[aesteban@localhost ~]$ echo ${INFO["name"]}
Angel Esteban Cool
[aesteban@localhost ~]$ 
[aesteban@localhost ~]$ INFO=([name]="Angel Cool" [website]="angelcool.net")
[aesteban@localhost ~]$ 
[aesteban@localhost ~]$ echo ${INFO["website"]}
angelcool.net
[aesteban@localhost ~]$

Loops

[aesteban@localhost ~]$ for i in $(seq 1 5); do echo This line corresponds to line $i.;done;
This line corresponds to line 1.
This line corresponds to line 2.
This line corresponds to line 3.
This line corresponds to line 4.
This line corresponds to line 5.
[aesteban@localhost ~]$ 
[aesteban@localhost ~]$ 
[aesteban@localhost ~]$ for i in {1..7}; do echo This is number $i.;done;
This is number 1.
This is number 2.
This is number 3.
This is number 4.
This is number 5.
This is number 6.
This is number 7.
[aesteban@localhost ~]$
[aesteban@localhost var]$ for i in `ls /var`;do echo $i;done;
 ...
[aesteban@localhost ~]$# looping through a list of servers
[aesteban@localhost ~]$for i in {1..5}; do ssh www-app0${i} "cd /var/www/html/barney.com && git pull origin live" ;done;
 

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