CSC139 Homework 5-Command Line interpreter Solved

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General rules: Create homework, compose specifications or any text by using a common document-creation tool, such as Microsoft® Word.

Hints: Refer to the wwweb or lecture notes for this class to design, implement, and debug correctly working SW solutions. Be concise, complete, and precise.

Abstract: Design, implement, explain, test, and debug a simple, but complete command-line interpreter named cli.

Detail: Design, implement, document, test and run a simple shell, known here as a command-line interpreter (cli). This tool is invoked via the cli command plus possible arguments. Commands are OS commands to be executed. Multiple commands are separated from one another by commas, and each may in turn require further arguments. Cli ‘knows’ a list of commands a-priori; they are predefined. When invoked, cli checks, whether the first argument is an included command. If so, cli confirms this via a brief message. If not, a contrary message is emitted, stating this is not one the predefined commands. After the message, cli executes all commands in the order listed. After executing the last command, cli prints the current working directory, i.e. it acts as if the pwd command had been issued. Sample runs are shown further below.


Multiple commands of cli must be separated from one another by commas. Possible parameters of any one command are separated from the command itself (and from possible further parameters) by white space. White space consists of blanks, tabs, or a combination, but at least 1 blank space. Here some sample runs with single and multiple commands; outputs are not shown here:


./cli pwd                           — looks like Unix command pwd; is your SW

./cli rm –f temp, mv temp ../temp1  — ditto: input to your running homework 5

./cli ls –la                        — another “single unix command”

./cli rm a.out, gcc sys.c, cp a.out cli


Cli starts out identifying itself, also naming you the author, and the release date. Then cli prints the list of all predefine commands. Finally, cli executes all commands input after the cli invocation. For your own debug effort, test your solution with numerous correct and also wrong inputs, including commas omitted, multiple commas, leading commas, illegals commands, other symbols instead of commas etc. No need to show or hand-in your test and debug work.


The output of the cli command “cli pwd” or “./cli pwd” should be as shown below, assuming your current working directory is ./classes_Sac_State/csc139. Here is the output of a sample run with a single command line argument:


herbertmayer$ ./cli pwd

hgm cli 4/12/2020

Legal commands:  cd exec exit gcc ls man more mv rm pwd sh touch which $path

2 strings passed to argv[]

next string is ‘pwd’

new string is ‘pwd ‘

1st cmd ‘pwd’ is one of predefined.



Here the output of another sample run, also with a single cli command:


herbertmayer$ ./cli ls

hgm cli 4/12/2020

Legal commands:  cd exec exit gcc ls man more mv rm pwd sh touch which $path

2 strings passed to argv[]

next string is ‘ls’

new string is ‘ls ‘

1st cmd ‘ls’ is one of predefined.

admin              cli.c         sac_state_yyy

backup_1_24_2020   docs          sac_state_hw

backup_3_9_2020    grades        sac_state_xxx

cli                l_notes



Interpretation of commands that cli handles can proceed through system(), executed from inside your C/C++ program cli.


List of all commands supported by your cli:


char * cmds[ ] = {