Advanced Programming in the UNIX Environment

Course CS631 - APUE

week-1

• simple-cat.c : cat command implementation unbuffered I/O
• simple-cat2.c : cat command implementation with buffered I/0
• simple-ls.c: ls command implementation with no arguments
• uidGid.c: printing user and group id's
• simple-shell.c : basic shell implementation
• simple-shell2.c : basic shell implementation with SIGINT handler

week-2

• openmax.c : determine number of open files a process can have using sysconf and getrlimit
• openex.c : illustrate opening of files
• lseek.c : check if a stdin is seekable.
• redir.c : output redirection via dup2.
• rwex.c : program to illustrate append.
• sync-cat.c : illustrate use of SYNC flag for immediate writes to disk.
• hole.c: it creates a hole in a file(sparse file).
• warmupExercise.c : find values of stdin, stdout, stderr.

homework-1

• hw1/bbcp: implemention of the barebones copy command.
• hw1/testcp.sh : test scipt for bbcp.
• hw1/bbcp.pdf : bbcp specification

week-3

• access.c - check if user has access to given file.
• chmod.c - change permissions on file.
• chown.c - change ownership of a file.
• setuid.c - raise/drop user privileges.
• size.c - print file size, block size of the given file.
• umask.c - setting default permissions with umask.

midTerm Project (Implementation of ls(1) command in NETBSD)

• midProject/ls.pdf - project specification.
• midProject/src, midProject/include - source files, header files.
• midProject/Makefile - build the project.(ls binary file is created)
• midProject/ls-test - test script.
• midProject/makelstest - test scrips.

week-4

• cd.c - to change current working directory.
• getpw.c - print userName/uid and iterate over all entries in /etc/passwd.
• groups.c - print groupName/gid and iterate over all group in system(/etc/groups).
• lns.c - create a soft link.
• rename.c - renaming a file (mv command).
• time.c - printing time in various formats.
• wait-unlink.c - to unlink a file. The space allocated to the file is cleared, once all the links pointing to the inode are deleted.

week-5

• compileChain - compiling files upto various stages(preprocessing, compile, assembly, linking).
• gdb-examples - debugging errors with gdb.
• make-examples - automating build with Make.

week-6

• memory-layout0.c - print the memory location of variable.
• memory-layout1.c - print the memory location of private variables, global variable and functions.
• memory-layout2.c - print the memory location of stack, heap, initialized data, unintialized data, text segment.
• memory-layout3.c - overflow the stack by by repeatedly calling function.
• memory-layout4.c - printing the memory of location environment variables.
• memory-layout5.c - accessing the last and first environment variable.
• memory-layout6.c - examining memory layout after updating a env variable to a larger value.
• memory-layout7.c - examining memory layout after addition of a new env variable.
• memory-layout8.c - examining memory layout after unsetting an env variable.
• entry1.c - print the address of function main.
• entry2.c - start the program from a different function apart from main.
• entry3.c - start the program from a different function and exit instead of return.
• entry4.c - comparing return statements between c89 and c11 standards.
• exit-handlers.c - terminaing a program using exit(),___ _exit(), abort().
• malloc.c - using malloc() and realloc();
• pid.c - get the process of current and the parent process.
• forkseek.c - illustrates sharing of file descriptors between parent and child processes.
• forkflush.c - illustrates sharing of buffers in between parent and child processes.
• zombies.c - illustrate creation of zombie process.

week-7

• sigusr.c - illustrates the use of signals handlers, by implementing signal handlers for SIGUSR1 and SIGUSR2
• signals1.c - illustrates interuption while executing a signal handler.
• signals2.c - illustrates the default behaviour of signals handlers.
• signals3.c - illustrates example of sigaction.
• signals4.c - illustrates the risk of buffered I/O from within the signal handler.
• reentrant.c - illustrates the risk of calling non-re-entrant functions from within the signal handler.
• eintr.c - illustrates the restart of a system call from being interupted.

week-8

• semdemo.c - illustrates the use of semaphores.
• shemdemo.c - illustrates the use of shared memory.
• msgrecv.c, msgsend.c - illustrates the use of message queues.
• mqrecv.c, mqsend.c - illustrates the use of POSIX message queues.
• pipe1.c - illustsrates echo msg | cat pipeline.
• pipe2.c - illustrates cat file.txt | ${PAGER:-/usr/bin/more}
• popen.c - same as pipe2.c but using popen(3).

homework-2

• hw2/command.c : pass a command to the shell and return stdout and stderr.
• hw2/driver.c : example driver program to run command.
• hw2/command.pdf : command specification The program uses the following:

• create two pipes, one for stdout, one for stderr of the command to execute
• ignore SIGINT, SIGQUIT; block SIGCHLD
• fork(2) a new process
• dup2(2) the respective file descriptors onto the write-ends of the pipes
• exec(3) the command in question
• read(2) from the read-ends of the pipes
• append output to the respective buffer, careful to not overflow them
• wait(3) for the process to terminate