Solution for Ch.8

#include

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#define BUFSIZE 128

#define oops( m, x ) { perror(m); exit(x); }

/*

A. The user types a.out

B. The shell creates a new process to run

the program.

C. The shell loads the program from disk

into the process.

D. The program runs in its process until done

*/

/*

while( ! end_of_input )

get command

execute command

wait for command to finish

*/

const int MAX_CHARS = 255;

const int MAX_ARGS = 20;

void get(char*);

void execute( char* );

char** parse( char*);

//int cd(char* directory);

int main(int ac, char *args[]) //ac stores number of arguments, args stores actual arguments

{

static int skip = 0;

char* command[MAX_ARGS+1];

char commandment[MAX_CHARS];

signal(SIGINT, SIG_IGN); // Ignore Ctrl-C

while(1)

{

get(commandment);

execute(commandment);

}

}

void execute(char* arglist)

/*

use fork and execvp and wait to do it

*/

{

char** split = parse(arglist);

int pid, exitstatus; // of child

int len;

int i = 0;

char buf[BUFSIZ]; // for reading end

int fd, apipe[2]; ;

char null = '\0';

pid = fork(); // make new process

char IORedirection = '\0';

switch( pid )

{

case -1:

perror( "fork failed" );

exit(1);

case 0:

while( split[++i] != '\0' )

{

if ( split[i][0] == '' || split[i][0] == '|' )

{

IORedirection = split[i][0];

break;

}

}

if ( IORedirection == '

{

close(0);

fd = open(split[i+1], O_RDONLY );

if ( fd == -1 )

{

printf("Error: File could not be opened!");

exit(1);

}

split[i] = '\0';

}

else if (IORedirection == '>' )

{

close(1);

fd = open( split[i+1], O_WRONLY | O_CREAT, 0744 );

if ( fd == -1 )

{

printf("Error: File could not be opened!");

exit(1);

}

split[i] = '\0';

}

if (IORedirection == '|' )

{

// get a pipe

if ( pipe ( apipe ) == -1 )

{

perror( "could not make pipe" );

exit(1);

}

printf( "Got a pipe! It has file descriptors: ( %d %d ) ",

apipe[0], apipe[1] );

split[i] = '\0';

/*

// read from stdin, write into pipe, read from pipe, print

while( fgets( buf, BUFSIZ, stdin ) )

{

len = strlen( buf );

// send down pipe

if ( write( apipe[1], buf, len ) != len )

{

perror( "writing to pipe" );

break;

}

// wipe

for ( i = 0; i

buf[i] = 'X';

// read from pipe

len = read( apipe[0], buf, BUFSIZ );

if ( len == -1 )

{

perror( "reading from pipe" );

break;

}

// send to stdout

if ( write( 1, buf, len ) != len )

{

perror( "writing to stdout" );

break;

}

}

*/

}

execvp( split[0], split ); // do it

// perror( "execvp failed" );

exit(1);

default:

while( wait( &exitstatus ) != pid );

printf( "child exited with status %d, %d ",

exitstatus>>8, exitstatus & 0377 );

}

}

char** parse( char* input)

{

int i = 0;

char** split = malloc( 256 );

// fgets reads the , so overwrite it

// input[strlen(input)-1] = '\0';

// get the first token

split[i] = strtok( input, " " );

// get the rest of them

while( split[++i] = strtok(NULL, " ") );

return split;

}

void get(char* commandment)

{

char *cd = "cd";

printf("$ "); // Prompt for command

fgets( commandment, MAX_CHARS, stdin );

commandment[strlen(commandment)-1] = '\0';

if ( strcmp( commandment, "exit" ) == 0 )

exit(1);

if ( strstr( commandment, cd ) != NULL )

{

char *directory = strtok(commandment," ");

directory = strtok(NULL," ");

if(chdir(directory) == -1) {

perror("Cannot change directory");

}

else

printf("Directory changed ");

}

}

Course Evaluation Student Support Services Hints and Technical Info Midterm Final a Search or enter website name Apple Disney ESPN Yahoo! Student Courses Online Storage E-Portfolio Organizations & Clubs ample Code Attached Files: ch10SampleCode.zip (4.921 KB) HW10 Due Tuesday, May 30th, 11:59 PM Late submissions not accepted. For this assignment, you will add support for i/o redirection and piping to the shell you wrote for the CH08 homework. That is to say, and I. Feel free to use the solution from Chapter 8 to get you started. For example, your shell should now support commands like this: ls -l file.txt cat file.txt I wc file.txt sort file.txt Reminder Recursion is a thing. Course Evaluation Student Support Services Hints and Technical Info Midterm Final a Search or enter website name Apple Disney ESPN Yahoo! Student Courses Online Storage E-Portfolio Organizations & Clubs ample Code Attached Files: ch10SampleCode.zip (4.921 KB) HW10 Due Tuesday, May 30th, 11:59 PM Late submissions not accepted. For this assignment, you will add support for i/o redirection and piping to the shell you wrote for the CH08 homework. That is to say, and I. Feel free to use the solution from Chapter 8 to get you started. For example, your shell should now support commands like this: ls -l file.txt cat file.txt I wc file.txt sort file.txt Reminder Recursion is a thing