Minishell

===============

Team Mates

• Abhishek Jain
• Pradyumna Kaushik

Software Requirements

• GCC version 5.2.0 and upwards.

Note: Any lower version may result in underfined behaviour including compilation errors and memory corruptions.

Instructions to run the shell

• Compile the source code using Makefile using the following command,

  make
  

  This should have created an executable called 'shell'

• Run the shell using the following command,

  ./shell
  

• To clean up the project, use the following command,

  make clean
  

Fallback Compilation Instructions if 'make' fails

NOTE: SKIP THIS SECTION IF make was successful i.e. if make did not throw errors.

• Compile the source code using the following command,

  gcc minish.c -o shell
  

Bugs

• regcomp() in regex.h: the regcomp() module is buggy as it "sometimes" results in malloc() error.
  Please note that IF THIS ERROR OCCURS WHILE TESTING, the shell source code does not contain any bugs.
  Its the library issue, as we believe the library is deprecated.
  Reason to use it was to detect the foreground and background commands.
  The approach of tokenization and detection may result in segmentation faults.
  For example: the following is a scenario that can result in a segmentation fault:

  minish>gcc test_sleep.c -o bin/test_sleep.o
  minish>ls
  segmentation fault
  

  Note that the segmentation fault occurs only when the -o option is used with the gcc command.
  This link has more information about this -- https://lists.ubuntu.com/archives/foundations-bugs/2012-May/089662.html

• Continuing a suspended process in foreground works fine, but after the process completes
  execution it goes into an infinite loop. You will need to hit <Ctrl-C> to get back the prompt.

References

http://stackoverflow.com/questions/19814906/which-child-process-send-sigchld http://stackoverflow.com/questions/2595503/determine-pid-of-terminated-process http://stackoverflow.com/questions/12587621/signal-handler-sa-sigaction-arguments http://www.gnu.org/software/libc/manual/html_node/Sigaction-Function-Example.html http://man7.org/linux/man-pages/man2/sigaction.2.html http://stackoverflow.com/questions/4200373/just-check-status-process-in-c https://en.wikipedia.org/wiki/Unix_signal http://man7.org/linux/man-pages/man2/getpid.2.html http://linux.die.net/man/3/tcsetpgrp http://stackoverflow.com/questions/1157700/how-to-wait-for-exit-of-non-children-processes http://stackoverflow.com/questions/1058047/wait-for-any-process-to-finish http://www.gnu.org/software/libc/manual/html_node/Job-Control.html https://ftp.gnu.org/old-gnu/Manuals/glibc-2.2.3/html_chapter/libc_27.html http://www.gnu.org/software/libc/manual/html_node/Implementing-a-Shell.html http://linuxcommand.org/lts0080.php http://linux.die.net/man/3/execvp http://www.csl.mtu.edu/cs4411.ck/www/NOTES/process/fork/exec.html http://linux.die.net/man/2/waitpid http://linux.die.net/man/3/waitpid https://www.mkssoftware.com/docs/man3/waitpid.3.asp https://support.sas.com/documentation/onlinedoc/sasc/doc/lr2/waitpid.htm http://stackoverflow.com/questions/21248840/example-of-waitpid-in-use http://linux.die.net/man/2/kill http://linux.die.net/man/3/kill http://tldp.org/LDP/lpg/node11.html http://www.gnu.org/software/libc/manual/html_node/Creating-a-Pipe.html http://man7.org/tlpi/code/online/diff/pipes/simple_pipe.c.html https://www.cs.cf.ac.uk/Dave/C/node23.html http://stackoverflow.com/questions/9493234/chdir-to-home-directory http://stackoverflow.com/questions/298510/how-to-get-the-current-directory-in-a-c-program http://linux.die.net/man/3/getcwd http://www.gnu.org/software/libc/manual/html_node/Working-Directory.html http://cboard.cprogramming.com/c-programming/100200-check-blank-spaces-string.html http://stackoverflow.com/questions/17259250/fwrite-doesnt-print-anything-to-stdout http://www.tutorialspoint.com/c_standard_library/c_function_fwrite.htm http://stackoverflow.com/questions/13377773/proper-way-to-handle-signals-other-than-sigint-in-python http://www.cons.org/cracauer/sigint.html http://www.cplusplus.com/forum/beginner/1501/ http://stackoverflow.com/questions/6970224/providing-passing-argument-to-signal-handler http://www.gnu.org/software/libc/manual/html_node/Permission-for-kill.html http://pubs.opengroup.org/onlinepubs/009695399/functions/getpgrp.html http://stackoverflow.com/questions/22422400/error-initialization-makes-pointer-from-integer-without-a-cast http://stackoverflow.com/questions/5582211/what-does-define-gnu-source-imply http://www.gnu.org/software/libc/manual/html_node/Feature-Test-Macros.html http://www.regular-expressions.info/repeat.html http://www.gnu.org/software/libc/manual/html_node/Process-Creation-Example.html http://stackoverflow.com/questions/28457525/how-do-you-kill-zombie-process-using-wait http://codereview.stackexchange.com/questions/20897/trim-function-in-c http://stackoverflow.com/questions/122616/how-do-i-trim-leading-trailing-whitespace-in-a-standard-way http://unix.stackexchange.com/questions/5642/what-if-kill-9-does-not-work https://major.io/2010/03/18/sigterm-vs-sigkill/ http://unix.stackexchange.com/questions/132224/is-it-possible-to-get-process-group-id-from-proc http://ubuntuforums.org/showthread.php?t=1430052 http://ubuntuforums.org/showthread.php?t=1749381 http://theunixshell.blogspot.com/2012/12/running-background-process-and.html http://stackoverflow.com/questions/21871325/execvp-system-call-not-executing http://www.computerhope.com/unix/ucsh.htm http://www.peope.net/old/regex.html ftp://ftp.gnu.org/old-gnu/Manuals/grep-2.4/html_chapter/grep_5.html http://regexr.com http://www.seeingwithc.org/topic7html.html http://stackoverflow.com/questions/1631450/c-regular-expression-howto http://stackoverflow.com/questions/18477153/c-compiler-warning-unknown-escape-sequence-using-regex-for-c-program http://stackoverflow.com/questions/1395177/regex-to-exclude-a-specific-string-constant https://blog.udemy.com/c-string-to-int/ http://stackoverflow.com/questions/3213827/how-to-iterate-over-a-string-in-c http://stackoverflow.com/questions/21592494/initializer-element-is-not-constant-error-for-no-reason-in-linux-gcc-compilin http://www.cplusplus.com/forum/general/8795/ http://pubs.opengroup.org/onlinepubs/009695399/functions/regcomp.html http://stackoverflow.com/questions/22573292/glibc-detected-a-out-double-free-or-corruption-out-0xbfe69600 http://cboard.cprogramming.com/c-programming/98173-regular-expression-tutorial-help.html http://www.gnu.org/software/libc/manual/html_node/Regexp-Cleanup.html#Regexp-Cleanup http://stackoverflow.com/questions/23031590/reading-from-pipe-into-buffer-character-by-character-find-the-size-of-data-in-pi http://www.cs.cornell.edu/Courses/cs414/2004su/homework/shell/shell.html http://brennan.io/2015/01/16/write-a-shell-in-c/ http://stackoverflow.com/questions/1500004/how-can-i-implement-my-own-basic-unix-shell-in-c