2 files changed, 216 insertions, 0 deletions
diff --git a/1088/CH24/EX24.3/Example3.sce b/1088/CH24/EX24.3/Example3.sce
new file mode 100755
index 000000000..5c4fc8e34
--- /dev/null
+++ b/1088/CH24/EX24.3/Example3.sce
@@ -0,0 +1,101 @@
+clear
+flag=1
+mode(-1)
+clc
+
+printf("Example 3    :    Show the effect of changing the childs environment and check its effect in parent \n")
+disp("****************************************************************")
+disp("Answer    :   ")
+disp("INSTRUCTIONS   : ")
+halt(' ')
+disp("1.These programs are part of systems programming PURELY in Unix and the commands have NO EQUIVALENT IN SCILAB")
+halt(' ')
+disp("2.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")
+halt(' ')
+disp("3.The outputs displayed here are just MOCK OUTPUTS which are DISPLAYED IN THE TEXTBOOK")
+halt(' ')
+disp("4.The inconvenience is regretted.")
+halt('.............Press [ENTER] to continue.....')
+halt("")
+clc
+printf("\tUNIX SHELL SIMULATOR(DEMO VERSION WITH PRELOADED COMMANDS)\n\n\n")
+i=0
+i=i+1;f(i)='/* Program: childenv.c -- Changes child'+ascii(39)+'s environment and then checks the effect in parent*/'
+i=i+1;f(i)='#include <stdio.h>'
+i=i+1;f(i)='#include <sys/types.h>'
+i=i+1;f(i)='#define PATH_LENGTH 30'
+i=i+1;f(i)=''
+i=i+1;f(i)='int main(void) {'
+i=i+1;f(i)='    pid_t pid;'
+i=i+1;f(i)='    int x = 100;'
+i=i+1;f(i)='    char newdir[PATH_LENGTH + 1]; /* Additional space required for \0*/'
+i=i+1;f(i)='    '
+i=i+1;f(i)='    getcwd(newdir, PATH_LENGTH);  /* Get current directory before fork */'
+i=i+1;f(i)='    printf('+ascii(34)+'BEFORE FORK -- Current directory: %s\n'+ascii(34)+', newdir);'
+i=i+1;f(i)='    '
+i=i+1;f(i)='    pid = fork ();'
+i=i+1;f(i)='    switch (pid) {'
+i=i+1;f(i)='        case -1:'
+i=i+1;f(i)='        perror('+ascii(34)+'fork'+ascii(34)+');'
+i=i+1;f(i)='        exit(1);                /*for error*/'
+i=i+1;f(i)='        case 0:  /*Child*/'
+i=i+1;f(i)='        printf('+ascii(34)+'CHILD -- Inherited value of x: %d\n'+ascii(34)+', x);'
+i=i+1;f(i)='        x=200;'
+i=i+1;f(i)='        printf('+ascii(34)+'CHILD -- Changed value of x: %d\n'+ascii(34)+', x);'
+i=i+1;f(i)='        printf('+ascii(34)+'CHILD -- Inherited value of PATH: %s\n'+ascii(34)+', getenv('+ascii(34)+'PATH'+ascii(34)+'));'
+i=i+1;f(i)='        setenv('+ascii(34)+'PATH'+ascii(34)+','+ascii(34)+'.'+ascii(34)+', 1);   /* Change PATH here; use putenv('+ascii(34)+'PATH=.'+ascii(34)+') */'
+i=i+1;f(i)='                                 /* if setenv() not supported */'
+i=i+1;f(i)='        printf('+ascii(34)+'CHILD -- New value of PATH: %s\n'+ascii(34)+', getenv('+ascii(34)+'PATH'+ascii(34)+'));'
+i=i+1;f(i)='        if (chdir('+ascii(34)+'/etc'+ascii(34)+') != -) {       /* '+ascii(34)+'cd'+ascii(34)+' to /etc */'
+i=i+1;f(i)='        getcwd(newdir, PATH_LENGTH);    /* Do a '+ascii(34)+'pwd'+ascii(34)+' */'
+i=i+1;f(i)='        printf('+ascii(34)+'CHILD -- Current directory changed to: %s\n'+ascii(34)+',newdir);'
+i=i+1;f(i)='        }'
+i=i+1;f(i)='        break;'
+i=i+1;f(i)='        exit(0);'
+i=i+1;f(i)='        default:/* Parent */'
+i=i+1;f(i)='        sleep(2);                      /* Allow child to complete */'
+i=i+1;f(i)='        getcwd(newdir, PATH_LENGTH);    /*Getting new directory */'
+i=i+1;f(i)='        printf('+ascii(34)+'PARENT -- Value of x after change by child: %d\n'+ascii(34)+',x);'
+i=i+1;f(i)='        printf('+ascii(34)+'PARENT -- Current directory is still: %s\n'+ascii(34)+', newdir);'
+i=i+1;f(i)='        printf('+ascii(34)+'PARENT -- Value of PATH is unchanged: %s\n'+ascii(34)+',getenv('+ascii(34)+'PATH'+ascii(34)+'));'
+i=i+1;f(i)='        exit(0);'
+i=i+1;f(i)='}'
+i=i+1;f(i)='}'
+n=i        
+    
+
+printf("\n\n$ cat childenv.c      # to open the file emp.lst")
+halt(' ')
+u=mopen('childenv.c','wt')
+for i=1:n
+    mfprintf(u,"%s\n",f(i))
+    printf("%s\n",f(i))
+end
+mclose(u)
+halt('')
+clc
+
+halt(' ')
+ printf("$ cc childenv.c")
+ halt(' ')
+ printf("$ a.out")
+ halt(' ')
+ printf("BEFORE FORK -- Current directory: /users1/home/staff/sumit")
+ printf("\nCHILD -- Inherited value of x: 100")
+ printf("\nCHILD -- Changed value of x:200")
+ printf("\nCHILD -- Inherited value of PATH: /usr/bin::/usr/local/bin:/usr/ccs/bin")
+ printf("\nCHILD -- New value of PATH: .")
+ printf("\nCHILD -- Current directory changed to: /etc")
+ printf("\nPARENT -- Value of x after change to child: 100")
+ printf("\nPARENT -- Current directory is still: /users1/home/staff/sumit")
+ printf("\nPARENT -- Value of PATH is unchanged: /usr/bin::/usr/local/bin::/usr/ccs/bin")
+ halt(' ')
+
+printf("\n\n\n$ exit        #To exit the current simulation terminal and return to Scilab console\n\n")
+halt("........# (hit [ENTER] for result)")
+//clc()
+
+printf("\n\n\t\t\tBACK TO SCILAB CONSOLE...\nLoading initial environment')
+sleep(1000)
+
+
diff --git a/1088/CH24/EX24.3/Result3.txt b/1088/CH24/EX24.3/Result3.txt
new file mode 100755
index 000000000..d27c2b578
--- /dev/null
+++ b/1088/CH24/EX24.3/Result3.txt
@@ -0,0 +1,115 @@
+ ans  =
+ 
+    1.  
+ 
+ 
+-->exec('Example3.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                    :                                                                            24   
+ 
+ Chapter Title                         :                              Systems programming II- Files   
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+Example 3    :    Show the effect of changing the childs environment and check its effect in parent 
+ 
+ ****************************************************************   
+ 
+ Answer    :      
+ 
+ INSTRUCTIONS   :    
+  
+ 1.These programs are part of systems programming PURELY in Unix and the commands have NO EQUIVALENT IN SCILAB   
+  
+ 2.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                                                                              
+  
+ 3.The outputs displayed here are just MOCK OUTPUTS which are DISPLAYED IN THE TEXTBOOK   
+  
+ 4.The inconvenience is regretted.   
+.............Press [ENTER] to continue.....	UNIX SHELL SIMULATOR(DEMO VERSION WITH PRELOADED COMMANDS)
+
+
+
+
+$ cat childenv.c      # to open the file emp.lst /* Program: childenv.c -- Changes child's environment and then checks the effect in parent*/
+#include <stdio.h>
+#include <sys/types.h>
+#define PATH_LENGTH 30
+
+int main(void) {
+    pid_t pid;
+    int x = 100;
+    char newdir[PATH_LENGTH + 1]; /* Additional space required for \0*/
+    
+    getcwd(newdir, PATH_LENGTH);  /* Get current directory before fork */
+    printf("BEFORE FORK -- Current directory: %s\n", newdir);
+    
+    pid = fork ();
+    switch (pid) {
+        case -1:
+        perror("fork");
+        exit(1);                /*for error*/
+        case 0:  /*Child*/
+        printf("CHILD -- Inherited value of x: %d\n", x);
+        x=200;
+        printf("CHILD -- Changed value of x: %d\n", x);
+        printf("CHILD -- Inherited value of PATH: %s\n", getenv("PATH"));
+        setenv("PATH",".", 1);   /* Change PATH here; use putenv("PATH=.") */
+                                 /* if setenv() not supported */
+        printf("CHILD -- New value of PATH: %s\n", getenv("PATH"));
+        if (chdir("/etc") != -) {       /* "cd" to /etc */
+        getcwd(newdir, PATH_LENGTH);    /* Do a "pwd" */
+        printf("CHILD -- Current directory changed to: %s\n",newdir);
+        }
+        break;
+        exit(0);
+        default:/* Parent */
+        sleep(2);                      /* Allow child to complete */
+        getcwd(newdir, PATH_LENGTH);    /*Getting new directory */
+        printf("PARENT -- Value of x after change by child: %d\n",x);
+        printf("PARENT -- Current directory is still: %s\n", newdir);
+        printf("PARENT -- Value of PATH is unchanged: %s\n",getenv("PATH"));
+        exit(0);
+}
+}
+ $ cc childenv.c $ a.out BEFORE FORK -- Current directory: /users1/home/staff/sumit
+CHILD -- Inherited value of x: 100
+CHILD -- Changed value of x:200
+CHILD -- Inherited value of PATH: /usr/bin::/usr/local/bin:/usr/ccs/bin
+CHILD -- New value of PATH: .
+CHILD -- Current directory changed to: /etc
+PARENT -- Value of x after change to child: 100
+PARENT -- Current directory is still: /users1/home/staff/sumit
+PARENT -- Value of PATH is unchanged: /usr/bin::/usr/local/bin::/usr/ccs/bin 
+
+
+$ 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)