bash script

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Some often used bash scripts techniques. Also an example script I wrote for my network homework which does some auto download testing.

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### to start a script:
# !/bin/bash

### to assign variable: (notice no space in between)
vname1='str'
vname2=1

### use assigned variable:
echo $vname1

### simple loop
while(( $int<=100))
do
  echo $int
  # do something here
  let "int++"
done

Suppose we name out script as myscript.sh, to run it, fisrt we givie it permission:

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$ chmod 755 myscript.sh
$ ./myscript.sh

Some some techniques (more will be added):

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### string quotes
NAME="John"
echo "Hi $NAME"  #=> Hi John
echo 'Hi $NAME'  #=> Hi $NAME

### Conditional execution:
git commit; git push 
git commit && git push 
git commit || echo "Commit failed"

Now an example:

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# !/bin/bash
echo start creating files

### create 25 4kb files
int=1
while(( $int<=25 ))
do
  echo $int
  dd if=/dev/urandom of=test/t$int bs=1000 count=4
  let "int++"
done

### create 25 60kb files
int=1
while(( $int<=25 ))
do
  echo $int
  dd if=/dev/urandom of=test/tt$int bs=1000 count=60
  let "int++"
done

echo done creating files

At the end, a very good reference link: https://devhints.io/bash

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