basicsys@mars~/lec2>ls -l total 24 drwx------ 4 basicsys basicsys 4096 Nov 13 17:06 dir2 -rw------- 1 basicsys basicsys 8 Nov 13 15:53 F2 -rw------- 1 basicsys basicsys 21 Nov 13 17:31 F3 -rw------- 1 basicsys basicsys 2736 Nov 13 20:41 lec2m.txt -rwx------ 1 basicsys basicsys 130 Nov 13 17:21 P2 -rwx------ 1 basicsys basicsys 80 Nov 13 17:28 P3 basicsys@mars~/lec2>ls dir2 F2 F3 lec2e.txt lec2m.txt P2 P3 basicsys@mars~/lec2>ls -a . .. dir2 F2 F3 .fff lec2e.txt lec2m.txt P2 P3 basicsys@mars~/lec2>ls -R .: dir2 F2 F3 lec2e.txt lec2m.txt P2 P3 ./dir2: dir2 dir3 ./dir2/dir2: dir3 F2 ./dir2/dir2/dir3: F1 F2 ./dir2/dir3: F1 F2 F25 basicsys@mars~/lec2>tree . |-- F2 |-- F3 |-- P2 |-- P3 |-- dir2 | |-- dir2 | | |-- F2 | | `-- dir3 | | |-- F1 | | `-- F2 | `-- dir3 | |-- F1 | |-- F2 | `-- F25 |-- lec2e.txt `-- lec2m.txt 4 directories, 12 files basicsys@mars~/lec2>tree dir2 dir2 |-- dir2 | |-- F2 | `-- dir3 | |-- F1 | `-- F2 `-- dir3 |-- F1 |-- F2 `-- F25 3 directories, 6 files basicsys@mars~/lec2/dir2>tree . . |-- dir2 | |-- F2 | `-- dir3 | |-- F1 | `-- F2 `-- dir3 3 directories, 3 files basicsys@mars~/lec2/dir2>rmdir dir3 basicsys@mars~/lec2/dir2>tree . `-- dir2 |-- F2 `-- dir3 |-- F1 `-- F2 2 directories, 3 files basicsys@mars~/lec2/dir2>tree . `-- dir2 `-- dir3 |-- F1 `-- F2 2 directories, 2 files basicsys@mars~/lec2/dir2>ls dir2 basicsys@mars~/lec2/dir2>rm F1 rm: cannot remove `F1': No such file or directory basicsys@mars~/lec2/dir2>rm -f F1 basicsys@mars~/lec2/dir2>rm dir2 rm: cannot remove `dir2': Is a directory basicsys@mars~/lec2/dir2>rm -f dir2 rm: cannot remove `dir2': Is a directory basicsys@mars~/lec2/dir2>tree . . `-- dir2 `-- dir3 |-- F1 `-- F2 2 directories, 2 files basicsys@mars~/lec2/dir2>rm -r dir4 rm: cannot remove `dir4': No such file or directory basicsys@mars~/lec2/dir2>rm -r dir2 basicsys@mars~/lec2/dir2>tree . 0 directories, 0 files basicsys@mars~/lec2>tree . . |-- F2 |-- F3 |-- P2 |-- P3 |-- dir2 |-- lec2e.txt `-- lec2m.txt 1 directory, 6 files b asicsys@mars~/lec2>cd dir2 basicsys@mars~/lec2/dir2>mkdir dir3 basicsys@mars~/lec2>tree . . |-- F2 |-- F3 |-- P2 |-- P3 |-- dir2 | `-- dir3 | `-- F1 |-- lec2e.txt `-- lec2m.txt 2 directories, 7 files basicsys@mars~/lec2>rm -i F2 rm: remove regular file `F2'? n basicsys@mars~/lec2>rm -i dir2 rm: cannot remove directory `dir2': Is a directory basicsys@mars~/lec2>rm -r -i dir2 rm: descend into directory `dir2'? y rm: descend into directory `dir2/dir3'? y rm: remove regular file `dir2/dir3/F1'? y rm: remove directory `dir2/dir3'? basicsys@mars~/lec2>mkdir dir2 mkdir: cannot create directory `dir2': File exists basicsys@mars~/lec2>mkdir dir4 basicsys@mars~/lec2>tree . |-- F2 |-- F3 |-- P2 |-- P3 |-- dir2 | `-- dir3 |-- dir4 |-- lec2e.txt `-- lec2m.txt 3 directories, 6 files basicsys@mars~/lec2>mkdir dir5/dir6 mkdir: cannot create directory `dir5/dir6': No such file o basicsys@mars~/lec2>mkdir dir4/dir6 basicsys@mars~/lec2>mkdir -p d1/d2/d3/d4/d5 basicsys@mars~/lec2>tree . |-- F2 |-- F3 |-- P2 |-- P3 |-- d1 | `-- d2 | `-- d3 | `-- d4 | `-- d5 |-- dir2 | `-- dir3 |-- dir4 | `-- dir6 |-- lec2e.txt `-- lec2m.txt 9 directories, 6 files basicsys@mars~/lec2/dir2>tree . |-- F1 `-- dir3 1 directory, 1 file basicsys@mars~/lec2/dir2>cp F1 F2 basicsys@mars~/lec2/dir2>tree . |-- F1 |-- F2 `-- dir3 1 directory, 2 files basicsys@mars~/lec2/dir2>cat F2 abcddd basicsys@mars~/lec2/dir2>tree . |-- F1 |-- F2 `-- dir3 |-- F1 |-- F2 `-- dir4 `-- F8 3 directories, 4 files basicsys@mars~/lec2/dir2>cp -r dir3 dir5 basicsys@mars~/lec2/dir2>cp -r dir3 dir5 basicsys@mars~/lec2/dir2>tree . |-- F1 |-- F2 |-- dir3 | |-- F1 | |-- F2 | `-- dir4 | `-- F8 `-- dir5 |-- F1 |-- F2 `-- dir4 `-- F8 6 directories, 6 files basicsys@mars~/lec2/dir2>cp -r dir3 dir5 basicsys@mars~/lec2/dir2>tree . |-- F1 |-- F2 |-- dir3 | |-- F1 | |-- F2 | `-- dir4 | `-- F8 `-- dir5 |-- F1 |-- F2 |-- dir3 | |-- F1 | |-- F2 | `-- dir4 | `-- F8 `-- dir4 `-- F8 9 directories, 8 files basicsys@mars~/lec2/dir2>cp -i F1 F2 cp: overwrite `F2'? n basicsys@mars~/lec2/dir2>tree . |-- F1 |-- F2 `-- dir5 |-- F1 |-- F2 |-- dir3 | |-- F1 | |-- F2 | `-- dir4 | `-- F8 `-- dir4 `-- F8 6 directories, 6 files basicsys@mars~/lec2/dir2>mv F* dir5/dir3/dir4 basicsys@mars~/lec2/dir2>tree . `-- dir5 |-- F1 |-- F2 |-- dir3 | |-- F1 | |-- F2 | `-- dir4 | |-- F1 | |-- F2 | `-- F8 `-- dir4 `-- F8 6 directories, 6 files basicsys@mars~/lec2/dir2>mv dir5/dir4 dir5/dir3 mv: cannot move `dir5/dir4' to `dir5/dir3/dir4': Directory basicsys@mars~/lec2/dir2>mv dir5/dir4 dir5/dir3/dir8 basicsys@mars~/lec2/dir2>tree . `-- dir5 |-- F1 |-- F2 `-- dir3 |-- F1 |-- F2 |-- dir4 | |-- F1 | |-- F2 | `-- F8 `-- dir8 `-- F8 6 directories, 6 files basicsys@mars~/lec2/dir2>x=8 basicsys@mars~/lec2/dir2>echo $x 8 basicsys@mars~/lec2/dir2>echo x x basicsys@mars~/lec2/dir2>echo $x 8 basicsys@mars~/lec2/dir2>y=$[10+$x] basicsys@mars~/lec2/dir2>echo $y 18 basicsys@mars~/lec2/dir2>echo $[10+$x] 18 basicsys@mars~/lec2/dir2>echo $[12+$z] -bash: 12+: syntax error: operand expected (error token is basicsys@mars~/lec2/dir2>y=$[12+$z] -bash: 12+: syntax error: operand expected (error token is basicsys@mars~/lec2/dir2>read x 777777 basicsys@mars~/lec2/dir2>echo $x 777777 basicsys@mars~/lec2/dir2>read x 777777 basicsys@mars~/lec2/dir2>echo $x 777777 basicsys@mars~/lec2/dir2>read x abcdeee basicsys@mars~/lec2/dir2>echo $x abcdeee basicsys@mars~/lec2/dir2>echo $[18+$x] 18 basicsys@mars~/lec2/dir2>cat P1 #!/bin/bash read x read y echo "the sum of the two numbers is: $[$x+$y]" basicsys@mars~/lec2/dir2>P1 6 10 the sum of the two numbers is: 16 basicsys@mars~/lec2/dir2>cat F1 10 13 basicsys@mars~/lec2/dir2>P1 < F1 the sum of the two numbers is: 23 basicsys@mars~/lec2/dir2>cat P2 #!/bin/bash sum=0 while read x do sum=$[$sum+$x] done echo "the sum of all numbers is: $sum" basicsys@mars~/lec2/dir2>P2 10 4 17 the sum of all numbers is: 31 basicsys@mars~/lec2/dir2>seq 10 >|F1 basicsys@mars~/lec2/dir2>cat F1 1 2 3 4 5 6 7 8 9 10 basicsys@mars~/lec2/dir2>P2 < F1 the sum of all numbers is: 55