Question

Write a SHELL SCRIPT:

Write a simple shell that is similar to what we have discussed in class. while (1) {//repeat forever type_prompt();//display prompt on screen read_command (command, parameters);//read input from terminal if (fork() != theta)//parent wait (NULL);//wait for child else{execve (command, parameters, theta);//execute command}} but contains enough code that it actually works so you can test it. For simplicity, you may assume that all commands are in the directory/bin.

Answer 1

#1 /bin/bash # for a line count program using bash # Usage: ./line. Count . sh file # Link filedescriptor 10 with stdin exec 10<&0 # stdin replaced with a file supplied as a first argument exec く $1 # remember the name of the input file in-$1 # init file-"current_line.txt'" let count-0 # this while loop iterates over all lines of the file while read LINE # increase line counter ((count++)) # write current line to a tmp file with name file (not needed for counting) echo $LINE > $file # this checks the return code of echo (not needed for writing; just for demo) if [ $? -ne 0 ] then echo "Error in writing to file $(filej; check its permissions!" fi done echo "Number of lines: $count" echo "The last line of the file is: cat $(file" # Note: You can achieve the same by just using the tool wc like this echo "Expected number of lines: wc -l Şin" # restore stdin from filedescriptor 10 # and close filedescriptor 10 exec 0<&10 18<&-

before above writing the script you must have a file "text_file.txt" in your current directory. you can get a sizable sample text file by typing: $ cp /home/msc/public/LinuxIntro/WaD.txt text_file.txt