basicsys@mars~/lec10>x=5

basicsys@mars~/lec10>xx=a

basicsys@mars~/lec10>echo ${x}x
5x

basicsys@mars~/lec10>echo ${xx}
a

basicsys@mars~/lec10>x=1234rrt

basicsys@mars~/lec10>echo ${#x}
7

basicsys@mars~/lec10>echo -n $x | wc -c
7

basicsys@mars~/lec10>expr match ababc "a+"
0

basicsys@mars~/lec10>expr match ababc "a\+"
1

basicsys@mars~/lec10>expr match ababc "ab\+"
2

basicsys@mars~/lec10>expr match ababc "(ab)\+"
0

basicsys@mars~/lec10>expr match ababc "\(ab\)\+"
ab

basicsys@mars~/lec10>expr match ababc "\(ab\)\+"
ab

basicsys@mars~/lec10>expr match ababc "\(\(ab\)\+\)"
abab

basicsys@mars~/lec10>expr match ababc "\(\(ab\)\+\)d"

basicsys@mars~/lec10>expr match ababc "ad"
0

basicsys@mars~/lec10>expr match ababc "\(\(ab\)\+\)"
abab

basicsys@mars~/lec10>expr ababc : "\(\(ab\)\+\)"
abab

basicsys@mars~/lec10>expr index abcde db
2

basicsys@mars~/lec10>expr index abcde de
4

basicsys@mars~/lec10>x=abcde

basicsys@mars~/lec10>echo ${x:2}
cde

basicsys@mars~/lec10>echo ${x:1:3}
bcd

basicsys@mars~/lec10>echo ${x:2:2}
cd

basicsys@mars~/lec10>echo ${x:2:1}
c

basicsys@mars~/lec10>echo ${x:2:0}

basicsys@mars~/lec10>echo ${x:2:-1}
-bash: -1: substring expression < 0

basicsys@mars~/lec10>echo $x
abcde

basicsys@mars~/lec10>echo ${x#a??}
de

basicsys@mars~/lec10>echo ${x#a*}
bcde

basicsys@mars~/lec10>echo ${x##a*}

basicsys@mars~/lec10>echo $x
abcde

basicsys@mars~/lec10>echo ${x#a??}
de

basicsys@mars~/lec10>echo ${x#a*}
bcde

basicsys@mars~/lec10>echo ${x##a*}

basicsys@mars~/lec10>x=abcdaf

basicsys@mars~/lec10>echo ${x#a*}
bcdaf

basicsys@mars~/lec10>echo ${x#*a}
bcdaf

basicsys@mars~/lec10>echo ${x##*a}
f

basicsys@mars~/lec10>echo ${x#b*}
abcdaf

basicsys@mars~/lec10>echo ${x#a*}
bcdaf

basicsys@mars~/lec10>echo $x
abcdaf

basicsys@mars~/lec10>echo ${x%*f}
abcda

basicsys@mars~/lec10>echo ${x%%*f}

basicsys@mars~/lec10>echo $x
abcdaf

basicsys@mars~/lec10>echo ${x/ab/zzzz}
zzzzcdaf

basicsys@mars~/lec10>x=${x}abq

basicsys@mars~/lec10>echo $x
abcdafabq

basicsys@mars~/lec10>echo ${x/ab/zzzz}
zzzzcdafabq

basicsys@mars~/lec10>echo ${x//ab/zzzz}
zzzzcdafzzzzq

basicsys@mars~/lec10>y=/home/cs/segel/basicsys/lec10/tmp1

basicsys@mars~/lec10>echo $y
/home/cs/segel/basicsys/lec10/tmp1

basicsys@mars~/lec10>echo ${y##*/}
tmp1

basicsys@mars~/lec10>echo ${y##*/}${y}
tmp1/home/cs/segel/basicsys/lec10/tmp1

basicsys@mars~/lec10>cat G1
#!/bin/bash
echo -n "" >|tmp
x=$(pwd)
for y in $(find $x -type f)
 do
  echo ${y##*/}${y} >> tmp
 done
sort tmp >| tmp1
for z in $(cat tmp1)
  do
   echo \/${z#*/}
  done

basicsys@mars~/lec10>G1 | more
/home/cs/segel/basicsys/lec10/eval
/home/cs/segel/basicsys/lec10/F1
/home/cs/segel/basicsys/lec10/oldlec10/F1
/home/cs/segel/basicsys/lec10/F2
/home/cs/segel/basicsys/lec10/oldlec10/F2
/home/cs/segel/basicsys/lec10/F3
/home/cs/segel/basicsys/lec10/oldlec10/F3
/home/cs/segel/basicsys/lec10/F3t
/home/cs/segel/basicsys/lec10/F4
/home/cs/segel/basicsys/lec10/oldlec10/F4
/home/cs/segel/basicsys/lec10/F
/home/cs/segel/basicsys/lec10/G1
/home/cs/segel/basicsys/lec10/H
/home/cs/segel/basicsys/lec10/H.rep
/home/cs/segel/basicsys/lec10/lec10e.txt
/home/cs/segel/basicsys/lec10/lec10e.txt.save

basicsys@mars~/lec10>echo a{b,c}d
abd acd

basicsys@mars~/lec10>echo a{b,c}{1,2}e
ab1e ab2e ac1e ac2e

basicsys@mars~/lec10>echo {2..6}
2 3 4 5 6

basicsys@mars~/lec10>echo {b..d}
b c d

basicsys@mars~/lec10>echo {b..e}
b c d e

basicsys@mars~/lec10>echo {b..e}{1..2}
b1 b2 c1 c2 d1 d2 e1 e2

basicsys@mars~/lec10>a=(${a[@]} "aa   bb")

basicsys@mars~/lec10>echo ${a[@]}
aa bb cc dd e aa bb

basicsys@mars~/lec10>echo "${a[@]}"
aa bb cc dd e aa   bb

basicsys@mars~/lec10>a=("aa   bb" "cc   dd" e)

basicsys@mars~/lec10>a=("${a[@]}" "aa   bb")

basicsys@mars~/lec10>echo "${a[@]}"
aa   bb cc   dd e aa   bb

basicsys@mars~/lec10>echo "${#a[@]}"
4

basicsys@mars~/lec10>echo ${#a[@]}
4
basicsys@mars~/lec10>

basicsys@mars~/lec10>for x in "${a[@]}" ; do echo "$x" ; done
aa   bb
cc   dd
e
aa   bb

basicsys@mars~/lec10>for x in ${a[@]} ; do echo "$x" ; done
aa
bb
cc
dd
e
aa
bb

basicsys@mars~/lec10>a=(1 2 3)

basicsys@mars~/lec10>echo ${a[2]}
3

basicsys@mars~/lec10>a=(1 2)

basicsys@mars~/lec10>echo ${a[2]}

basicsys@mars~/lec10>a=(1 2 3)

basicsys@mars~/lec10>echo ${a[2]}
3

basicsys@mars~/lec10>a=50

basicsys@mars~/lec10>echo ${a[2]}
3

basicsys@mars~/lec10>echo ${a[@]}
50 2 3

basicsys@mars~/lec10>echo ${b[10]}
200

basicsys@mars~/lec10>b=("${b[@]}")

basicsys@mars~/lec10>echo ${b[@]}
200 300

basicsys@mars~/lec10>echo ${b[0]}
200

basicsys@mars~/lec10>echo ${b[1]}
300

basicsys@mars~/lec10>a=({1..8})

basicsys@mars~/lec10>echo ${a[@]:2}
3 4 5 6 7 8

basicsys@mars~/lec10>echo ${a[@]:2:2}
3 4

basicsys@mars~/lec10>a[9]=9

basicsys@mars~/lec10>echo ${a[@]:2}
3 4 5 6 7 8 9


basicsys@mars~/lec10>a=(abc abd ababe)

basicsys@mars~/lec10>echo ${a[@]/#a?}
c d abe

basicsys@mars~/lec10>echo ${a[@]/%b?}
a a aba

basicsys@mars~/lec10>echo ${a[@]/%%b?}
abc abd ababe

basicsys@mars~/lec10>echo ${a[@]/#a*}


basicsys@mars~/lec10>echo "${a[@]/a/zzz}"
zzzbc zzzbd zzzbabe

basicsys@mars~/lec10>echo "${a[@]//a/zzz}"
zzzbc zzzbd zzzbzzzbe

basicsys@mars~/lec10>a=({1..7})

basicsys@mars~/lec10>echo ${a[@]}
1 2 3 4 5 6 7

basicsys@mars~/lec10>unset a[2]

basicsys@mars~/lec10>echo ${a[@]}
1 2 4 5 6 7

basicsys@mars~/lec10>unset a

basicsys@mars~/lec10>echo ${a[@]}