CS810D Advanced Programming in the UNIX Environment
Fall 2008
Quiz 4


FULL NAME                       ______________________________________


USERNAME                        ______________________________________


1) Which of the following is the main feature of non-blocking I/O? (2 points)

a) typical input/output calls return EWOULDBLOCK if they cannot complete
   immediately

b) the process receives SIGIO if a typical input/output call cannot complete
   immediately

c) the kernel sends EINPROGRESS to all other processes currently performing
   typical input/output


Correct answer: (a)



2) Give an example of a system call that may block and indicate under what
   circumstances it will block. (2 points)


Possible correct answer:  read(2) from a pipe/fifo/socket when no data is
available (yet).



3) Name three things that a daemon process should do. (3 points)

Some correct answers:

- fork off parent
- change umask
- become session leader
- change cwd
- close or redirect file desriptors
- open logs


4) Name two sources from which a syslog daemon may collect messages. (2
   points)

- kernel messages via /dev/klog
- library calls to syslog(3)
- UDP socket (port 514)



5) Give two examples each (ie four in total) of a syslog facility and a
   syslog level. (4 points)

Facilities:
LOG_AUTH, LOG_AUTHPRIV, LOG_CRON, LOG_DAEMON, LOG_FTP, LOG_KERN, LOG_LPR,
LOG_MAIL, LOG_NEWS, LOG_SYSLOG, LOG_USER, LOG_UUCP, LOG_LOCAL[0-7]

Level:
LOG_EMERG, LOG_ALERT, LOG_CRIT, LOG_ERR, LOG_WARNING, LOG_NOTICE, LOG_INFO,
LOG_DEBUG



6) Name the four steps completed (by separate tools, actually) in the
   compilation process. (4 points)


Preprocessing (cpp), Compilation (cc), Assembly (as), Linking (ld).


7)  Consider the following Makefile:   (3 points)

PROG=       cp
OBJS=       cp.o utils.o
CFLAGS=     -Wall -g
CC=         cc

all: ${PROG}

${PROG}: ${OBJS}
        ${CC} ${LDFLAGS} ${OBJS} -o ${PROG}

cp.o:   extern.h
utils.o:extern.h


Write down the exact commands executed after invoking running

$ CC=gcc make


Solution:
cc -Wall -g  -c cp.c
cc -Wall -g  -c utils.c
cc  cp.o utils.o -o cp

The definition in the Makefile overwrites the definition in the environment.
Note the difference if you had run:

$ make CC=gcc
gcc -Wall -g  -c cp.c
gcc -Wall -g  -c utils.c
gcc  cp.o utils.o -o cp

Here the definition on the command-line *after* the 'make' command overwrites
the definition in the Makefile.