#!/bin/bash
echo Hello!

test@osboxes:~$ script.sh
script.sh: command not found

test@osboxes:~$ ./script.sh
-bash: ./script.sh: Permission denied

test@osboxes:~$ ls -l script.sh
-rw-rw-r-- 1 test test 22 Nov  9 05:27 script.sh

test@osboxes:~$ chmod a+x script.sh

test@osboxes:~$ chmod ug+rx script.sh

test@osboxes:~$ chmod a-w script.sh

test@osboxes:~$ chmod 754 script.sh

test@osboxes:~$ ls -la script.sh
-rwxr-xr-- 1 test test 22 Nov  9 05:27 script.sh

test@osboxes:~$ ./script.sh
Hello!

#!/bin/bash
echo Hello, $USER!
printf "Specified City is: %s, Country is: %s\n" $1 $2

test@osboxes:~$ chmod u+x script1.sh
test@osboxes:~$ ./script1.sh Moscow Russia
Hello, test!
Specified City is: Moscow, Country is: Russia

test@osboxes:~$ ./script1.sh "San Francisco" "United States"
Hello, test!
Specified City is: San Francisco, Country is: United States

printf "Specified City is: %s, Country is: %s\n" "$1" "$2"

COUNTRY=RUSSIA
echo $COUNTRY

if [ <условие> ]
then
  <команда1>
else
  <команда2>
fi

#!/bin/bash
echo Hello, $USER!
echo -n "Enter string: "
read str
if [ ${#str} -lt 8 ]
then
  echo String is too short
else
  echo String is ok
fi

test@osboxes:~$ ./script2.sh
Hello, test!
Enter string: abcde
String is too short
test@osboxes:~$ ./script2.sh
Hello, test!
Enter string: abcdefgh
String is ok

#!/bin/bash
echo Hello, $USER!
echo -n "Enter string: "
read str
if [ ${#str} -lt 8 ]
then
  echo String is too short
else
  if [ ${#str} -gt 16 ]
  then
    echo String is too long
  else
    echo String is ok
  fi
fi

test@osboxes:~$ ./script2.sh
Hello, test!
Enter string: abcdef
String is too short
test@osboxes:~$ ./script2.sh
Hello, test!
Enter string: abcdefghijklmnopqrstuv
String is too long
test@osboxes:~$ ./script2.sh
Hello, test!
Enter string: abcdefghijkl
String is ok

case "$переменная" in
"$значение1" )
<команда1>;;
"$значение2" )
<команда2>;;
esac

#!/bin/bash
echo -n "Enter the name of planet: "
read PLANET
echo -n "The $PLANET has "
case $PLANET in
  Mercury | Venus ) echo -n "no";;
  Earth ) echo -n "one";;
  Mars ) echo -n "two";;
  Jupiter ) echo -n "79";;
  *) echo -n "an unknown number of";;
esac
echo " satellite(s)."

test@osboxes:~$ ./script3.sh
Enter the name of planet: Mercury
The Mercury has no satellite(s).
test@osboxes:~$ ./script3.sh
Enter the name of planet: Venus
The Venus has no satellite(s).
test@osboxes:~$ ./script3.sh
Enter the name of planet: Earth
The Earth has one satellite(s).
test@osboxes:~$ ./script3.sh
Enter the name of planet: Mars
The Mars has two satellite(s).
test@osboxes:~$ ./script3.sh
Enter the name of planet: Jupiter
The Jupiter has 79 satellite(s).
test@osboxes:~$ ./script3.sh
Enter the name of planet: Alpha555
The Alpha555 has an unknown number of satellite(s).

#!/bin/bash
echo -n "Enter key: "
read -n 1 key
echo
case "$key" in
  [a-z]   ) echo "Lowercase";;
  [A-Z]   ) echo "Uppercase";;
  [0-9]   ) echo "Digit";;
  *       ) echo "Something else";;
esac

test@osboxes:~$ ./a.sh
Enter key: t
Lowercase
test@osboxes:~$ ./a.sh
Enter key: P
Uppercase
test@osboxes:~$ ./a.sh
Enter key: 5
Digit
test@osboxes:~$ ./a.sh
Enter key: @
Something else

for [ <условие> ] do <команды> done

while [ <условие> ] do <команды> done

until [ <условие> ] do <команды> done

#!/bin/bash
PLANET="-"
while [ $PLANET != "EXIT" ]
do
  echo -n "Enter the name of planet: "
  read PLANET
  if [ $PLANET != "EXIT" ]
  then.
    echo -n "The $PLANET has "
    case $PLANET in
      Mercury | Venus ) echo -n "no";;
      Earth ) echo -n "one";;
      Mars ) echo -n "two";;
      Jupiter ) echo -n "79";;
      *) echo -n "an unknown number of";;
    esac
  echo " satellite(s)."
  fi
done

test@osboxes:~$ ./script4.sh
Enter the name of planet: Earth
The Earth has one satellite(s).
Enter the name of planet: Jupiter
The Jupiter has 79 satellite(s).
Enter the name of planet: Planet123
The Planet123 has an unknown number of satellite(s).
Enter the name of planet: EXIT

#!/bin/bash
rm *.dat
echo -n "File count: "
read count
for (( i=1; i<=$count; i++ ))
do
  head -c ${i}M </dev/urandom >myfile${i}mb.dat
done
ls -l *.dat
echo -n "Delete file greater than (mb): "
read maxsize
for f in *.dat
do
  size=$(( $(stat -c %s $f) /1024/1024))
  if [ $size -gt $maxsize ]
  then.
    rm $f
    echo Deleted file $f
  fi
done
ls -l *.dat
read

test@osboxes:~$ ./script5.sh
File count: 10
-rw-rw-r-- 1 test test 10485760 Nov  9 08:48 myfile10mb.dat
-rw-rw-r-- 1 test test  1048576 Nov  9 08:48 myfile1mb.dat
-rw-rw-r-- 1 test test  2097152 Nov  9 08:48 myfile2mb.dat
-rw-rw-r-- 1 test test  3145728 Nov  9 08:48 myfile3mb.dat
-rw-rw-r-- 1 test test  4194304 Nov  9 08:48 myfile4mb.dat
-rw-rw-r-- 1 test test  5242880 Nov  9 08:48 myfile5mb.dat
-rw-rw-r-- 1 test test  6291456 Nov  9 08:48 myfile6mb.dat
-rw-rw-r-- 1 test test  7340032 Nov  9 08:48 myfile7mb.dat
-rw-rw-r-- 1 test test  8388608 Nov  9 08:48 myfile8mb.dat
-rw-rw-r-- 1 test test  9437184 Nov  9 08:48 myfile9mb.dat
Delete file greater than (mb): 5
Deleted file myfile10mb.dat
Deleted file myfile6mb.dat
Deleted file myfile7mb.dat
Deleted file myfile8mb.dat
Deleted file myfile9mb.dat
-rw-rw-r-- 1 test test 1048576 Nov  9 08:48 myfile1mb.dat
-rw-rw-r-- 1 test test 2097152 Nov  9 08:48 myfile2mb.dat
-rw-rw-r-- 1 test test 3145728 Nov  9 08:48 myfile3mb.dat
-rw-rw-r-- 1 test test 4194304 Nov  9 08:48 myfile4mb.dat
-rw-rw-r-- 1 test test 5242880 Nov  9 08:48 myfile5mb.dat