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+---- Thread: [Shell] Writing a simple bash command line shell in C (/showthread.php?tid=6047828)
Writing a simple bash command line shell in C - Kaydotx - Feb 8, 2020
I have a university assignment due in 22 hours,
my task is to design a simple command line shell that meets the following criteria
The shell must support the following internal commands:
i. cd <directory> - Change the current default directory to
<directory>. If the <directory> argument is not present, report the
current directory. If the directory does not exist an appropriate error
should be reported. This command should also change the PWD
environment variable.
ii. clr - Clear the screen.
iii. dir <directory> - List the contents of directory <directory>.
iv. environ - List all the environment strings.
v. echo <comment> - Display <comment> on the display followed by a new
line (multiple spaces/tabs may be reduced to a single space).
vi. help - Display the user manual using the more filter.
vii. pause - Pause operation of the shell until 'Enter' is pressed.
viii.
quit - Quit the shell.
ix. The shell environment should contain shell=<pathname>/myshell where
<pathname>/myshell is the full path for the shell executable (not a
hardwired path back to your directory, but the one from which it was
executed).
2. All other command line input is interpreted as program invocation,
which should be done by the shell forking and execing the programs as its own
child processes. The programs should be executed with an environment that
contains the entry: parent=<pathname>/myshell where <pathname>/myshell
is as described in 1.ix. above.
3. The shell must be able to take its command line input from a file. That
is, if the shell is invoked with a command line argument
myshell batchfile
then batchfile is assumed to contain a set of command lines for the shell to
process. When the end-of-file is reached, the shell should exit. Obviously, if
the shell is invoked without a command line argument, it solicits input from the
user via a prompt on the display.
4. The shell must support i/o-redirection on either or both stdin and/or
stdout. That is, the command line
programname arg1 arg2 < inputfile > outputfile
will execute the program programname with arguments arg1 and arg2, the
stdin FILE stream replaced by inputfile and the stdout FILE stream replaced
by outputfile.
stdout redirection should also be possible for the internal commands
dir, environ, echo, & help.
With output redirection, if the redirection character is > then the outputfile is
created if it does not exist and truncated if it does. If the redirection token is >>
then outputfile is created if it does not exist and appended to if it does.
5. The shell must support background execution of programs. An ampersand (&) at
the end of the command line indicates that the shell should return to the command
line prompt immediately after launching that program
6. The command line prompt must contain the pathname of the current
directory.
Submission
A makefile is required. All files in your submission will be copied to the same
directory; therefore, do not include any paths in your makefile. The makefile
should include all dependencies that build your program. If a library is included,
your makefile should also build the library.
from my understanding the shell has to be coded in C, i have no knowledge whatsoever.
can anyone provide me with help or resources?
Thanks.
Also the bash shell has to run via UNIX
RE: Writing a simple bash command line shell in C - smelly_poop07 - Feb 10, 2020
You posted this in the wrong section as you specified this has to be made in C but you're posting in the Batch, Bash & CLI section
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