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ans =
1.
-->exec('Example2.sci')
-->clear
-->flag=1
flag =
1.
-->mode(-1)
Current date is 23-Jun-2013
Welcome to the Textbook Companionship Project 2013
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Book Title : UNIX CONCEPTS AND APPLICATIONS
Book Edition : 4
Book Author : Sumitabha Das
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Code Author : Pranav Bhat T
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Chapter Number : 23
Chapter Title : Systems programming I- Files
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Example 2 : Show the method of reversing a file using lseek
****************************************************************
Answer :
INSTRUCTIONS :
1.These programs are part of systems programming in Unix and the commands have NO EQUIVALENT IN SCILAB
2.However if possible some selected programmes have been TRIED TO BE IMPLEMENTED
3.For most of the programmes whose equivalent is NOT THERE IN SCILAB,only the output has been printed as given in the textbook w
ith no interactive input as in the programme below
4.However the .c files which are displayed here are also made into a seperate file.If you are a unix user then try compiling and
running the programme with gcc or cc compiler
5.The inconvenience is regretted.
.............Press [ENTER] to continue..... UNIX SHELL SIMULATOR(DEMO VERSION WITH PRELOADED COMMANDS)
$ cat reverse_read.c # to open the file emp.lst /* Program: reverse_read.c -- Reads a file in reverse - uses lseek */
#include <fcntl.h> /* For O_RONLY */
#include <unistd.h> /* For STDOUT_FILENO */
int main(int argc, char **argv) {
char buf; /* Single-character buffer; will make */
int size, fd; /* I/O inefficient. See Section 23.4 */
fd= open(argv[1], O_RDONLY);
size = lseek(fd, -1, SEEK_END); /* Pointer taken to EOF - 1 ... */
while (size-- >= 0) { /* ... so siz = file size - 1 */
read(fd, &buf, 1); /* Read one character at a time */
write(STD_FILENO, &buf, 1); /* and write it immediately */
lseek(fd, -2, SEEK_CUR); /* Now move the file pointer back */
} /* by two characters */
/* exit(0); */ /* done deliberately */
}
$ ls
ans =
!vv.txt !
! !
!reverse_read.c !
! !
!Result2.txt !
! !
!Example9.sci !
! !
!Example8.sci !
! !
!Example7.sci !
! !
!Example6.sci !
! !
!Example5.sci !
! !
!Example4.sci !
! !
!Example3.sci !
! !
!Example2.sci !
! !
!Example13.sci !
! !
!Example12.sci !
! !
!Example11.sci !
! !
!Example10.sci !
! !
!ex9 !
! !
!ex8 !
! !
!ex7 !
! !
!ex6 !
! !
!ex5 !
! !
!ex4 !
! !
!ex3 !
! !
!ex2 !
! !
!ex13 !
! !
!ex12 !
! !
!ex11 !
! !
!ex10 !
! !
!ex1 !
$ cat vv.txt Warning: file 'vv.txt' already opened in Scilab.
hi there
How are you
I am fine
Thank You
Good Bye
$ cc reverse_read.c$ a.out vv.txt
......a blank line... The terminating \n of the last lineWarning: file 'vv.txt' already opened in Scilab.
eyB dooG
uoY knahT
enif ma I
uoy era woH
ereht i
$ exit #To exit the current simulation terminal and return to Scilab console
........# (hit [ENTER] for result)
BACK TO SCILAB CONSOLE...
Loading initial environment
-->diary(0)
|
