basicsys@mars~>echo -n aabbaba |egrep -o a
a
a
a
a

basicsys@mars~>echo -n aabbaba |egrep -o a | wc -l
4

basicsys@mars~>echo aba | tr a "\n" | wc -l
3

basicsys@mars~>echo -n aba | tr a "\n" | wc -l
2

basicsys@mars~>x=$(echo -n aba |wc -c)

basicsys@mars~>y=$(echo -n aba | tr -d a | wc -c)

basicsys@mars~>echo $[$x-$y]

basicsys@mars~/lec9>ls -l P1
-rwx------ 1 basicsys basicsys 170 Dec 17 10:15 P1

basicsys@mars~/lec9>ls -l --time=atime P1
-rwx------ 1 basicsys basicsys 170 Dec 21 20:51 P1

basicsys@mars~/lec9>ls -l --time=ctime P1
-rwx------ 1 basicsys basicsys 170 Dec 17 10:16 P1
basicsys@mars~/lec9>chmod u-x P1

basicsys@mars~/lec9>ls -l --time=ctime P1
-rw------- 1 basicsys basicsys 170 Dec 25 19:08 P1

basicsys@mars~/lec9>ls -l P1
-rw------- 1 basicsys basicsys 170 Dec 17 10:15 P1

basicsys@mars~/lec9>cat P1
echo "the first parameter is $1"
echo "the second parameter is $2"
echo "the number of parameters $#"
echo "all the parameters are: $*"
echo "all the parameters are: $@"

basicsys@mars~/lec9>ls -l --time=atime P1
-rw------- 1 basicsys basicsys 170 Dec 25 19:08 P1

basicsys@mars~/lec9>date
Tue Dec 25 19:09:30 IST 2012

basicsys@mars~/lec9>echo aa >> P1
basicsys@mars~/lec9>ls -l P1
-rw------- 1 basicsys basicsys 173 Dec 25 19:10 P1

basicsys@mars~/lec9>ls -l --time=ctime P1
-rw------- 1 basicsys basicsys 173 Dec 25 19:10 P1
basicsys@mars~/lec9>

basicsys@mars~/lec9>cat P1
#!/bin/bash
for x in $*
 do
  echo "$x"
 done
for x in $@
 do
  echo "$x"
 done
for x in "$*"
 do
  echo "$x"
 done
for x in "$@"
 do
  echo "$x"
 done

basicsys@mars~/lec9>P1 "ab   cd"  "ef   gh"
ab
cd
ef
gh
ab
cd
ef
gh
ab   cd ef   gh
ab   cd
ef   gh

basicsys@mars~/lec9>cat P2
#!/bin/bash
echo $*
echo $#
shift
echo $*
echo $#
shift
echo $*
echo $#

basicsys@mars~/lec9>P2 10 20 30 40
10 20 30 40
4
20 30 40
3
30 40
2

basicsys@mars~/lec9>cat P3
#!/bin/bash
s=0
while [ $# -ge 1 ]
 do
  s=$[$s+$1]
  shift
 done
echo $s

basicsys@mars~/lec9>P3 10 20 30
60

basicsys@mars~/lec9>cat P16
#!/bin/bash
read x
case $x in
 a)
  echo "you typed a";;
 b|c)
  echo "you typed b or c";;
 g*)
  echo "you typed a string that starts with g";;
 f??)
  echo "you typed a string that starts with f followd by exa
  echo " two charactres";;
 *)
  echo "you typed nothing of the first options";;
esac

basicsys@mars~/lec9>P16
yyyy
you typed nothing of the first options

basicsys@mars~/lec9>P16
a
you typed a

basicsys@mars~/lec9>P16
b
you typed b or c

basicsys@mars~/lec9>P16
fabc
you typed nothing of the first options

basicsys@mars~/lec9>P16
f1u
you typed a string that starts with f followd by exactly
 two charactres

basicsys@mars~/lec9>cat P16.1
#!/bin/bash
case "$1" in
 [a-c]r[a-c])
  echo "you typed one of a,b,c followd by r followd"
  echo "  bye one of a,b,c";;
 *aef[wqs]?)
  echo "you typed any sring followd by aef followd by"
  echo "one of w,q,s followd by one character";;
 ?)
  echo "you typed exactly one character";;
 ?*)
  echo "you typed at least one chacter";;
 *)
  echo "you typed nothing of the first options";;
esac

basicsys@mars~/lec9>P16.1 abcrabc
you typed at least one chacter

basicsys@mars~/lec9>P16.1 arc
you typed one of a,b,c followd by r followd
  bye one of a,b,c

basicsys@mars~/lec9>P16.1 rzqwefzaefw
you typed at least one chacter

basicsys@mars~/lec9>P16.1 rzqwefzaefwtr
you typed at least one chacter

basicsys@mars~/lec9>P16.1 rzqwefzaefwt
you typed any sring followd by aef followd by
one of w,q,s followd by one character

basicsys@mars~/lec9>P16.1 w
you typed exactly one character

basicsys@mars~/lec9>P16.1
you typed nothing of the first options

basicsys@mars~/lec9>tree t
t
|-- d1
|   |-- d3
|   |   |-- a1
|   |   |-- f2
|   |   `-- f3
|   `-- f4
|-- d2
|   `-- d3
|       `-- f5
`-- f1

5 directories, 5 files

basicsys@mars~/lec9>find t -name f5 -print
t/d2/d3/f5

basicsys@mars~/lec9>find t -name f* -print
t/d1/f4
t/d1/d3/f2
t/d1/d3/f3
t/f1
t/d2/d3/f5

basicsys@mars~/lec9>find t -name f* -print -print
t/d1/f4
t/d1/f4
t/d1/d3/f2
t/d1/d3/f2
t/d1/d3/f3
t/d1/d3/f3
t/f1
t/f1
t/d2/d3/f5
t/d2/d3/f5

basicsys@mars~/lec9>find t -name f*
t/d1/f4
t/d1/d3/f2
t/d1/d3/f3
t/f1
t/d2/d3/f5

basicsys@mars~/lec9>ls -l t
total 12
drwx------ 3 basicsys basicsys 4096 Dec 24 18:17 d1
drwx------ 3 basicsys basicsys 4096 Dec 17 10:40 d2
-rw------- 1 basicsys basicsys   37 Dec 24 18:19 f1

basicsys@mars~/lec9>find t -size 37c
t/f1

basicsys@mars~/lec9>find t -size +37c
t
t/d1
t/d1/d3
t/d1/d3/f2
t/d1/d3/f3
t/d1/d3/a1
t/d2
t/d2/d3

basicsys@mars~/lec9>find t -size -37c
t/d1/f4
t/d2/d3/f5

basicsys@mars~/lec9>find -name a* -o -size 37c
./t/d1/d3/a1
./t/f1

basicsys@mars~/lec9>find t -name a* -size 37c

basicsys@mars~/lec9>find t \( -name a* -o -size 37c \) -mmin -100

basicsys@mars~/lec9>find t \( -name a* -o -size 37c \) -mmin +100
t/d1/d3/a1
t/f1