CSI 3336 - Final Exam

gdb - steps through program one step at a time

n (next)

A product that can be used to determine and find memory leaks

Valgrind

Create and maintain static libraries

ar (archive)

A single copy of a library loaded into memory

Shared libraries

First call to open returns

3

Get to root directory

/

File descriptor

fd

Function that returns a different value every second

time()

Output exit status of most recently run code

echo $?

Relative path to home directory

~

When matching file names in shell, what matches any single character? (example of file name expansion)

?

Developer of Linux

Linus Torvalds, University of Helsinki

GNU

GNU's Not Unix

Where was C developed?

Bell Laboratories

Libraries in Linux are known as archives. What is the typical file extension?

.a

Create directory named 'cs3336' (located back one directory in myClass)

mkdir ../myClasses/cs3336

Print all files named fooxx (f case insensitive, xx - two base 10 digits) to printer ecs312

lpr -P ecs312 [Ff]oo[0-9][0-9]

Swap order of 1st and last name in a file named classList.txt

sed -E 's/(.)(.)/\2\1/'

Find the max value using a bash shell script

#!/bin/bash

maxValue()

{

big = $1

for val

do

if [[ $big -lt $val ]]

then

big = $val

done

echo $big

}

ret = $(maxValue 15 18)

Write a makefile for project (myprog)

- Must have ability to clean, use at least 1 macro, force gnu89 standard on all compiles

cc = gcc -std=gnu89

OBJ = main.o a.o b.o

myprog: $(OBJ)

$(cc) -o myproj $(OBJ)

clean:

rm myprog $(OBJ)

main.o: main.c a.h b.h

$(cc) -c main.c

a.o: a.c a.h b.h

$(cc) -c a.c

b.o: b.c b.h

$(cc) - c b.c

What is a system call?

Fundamental interface between an application and the Linux kernel.

How are they similar/different from other functions?

Other functions (wrapper functions) invoke system calls. System calls perform the same functions as library functions, but at a different layer of abstraction.

When would you choose to use a system call versus another function?

When working with file descriptors and pipes, system calls must be used to read and write.

Using only system calls for I/O, write readADigit()

- reads individual digit, give int back to calling function if it exists

readADigit(int fd)

{

int answer = -1;

char ch;

if ((read(fd, &ch, 1) != -1) || ch < '0' || ch > '9')

{

answer = -1;

}

else

{

answer = ch - '0';

}

return answer;

}

Code fragment that uses getopt() to count number of v options given on command land and prints count

-v option: get increasingly verbose diagnostic output

int main( int argc, char *argv[] )

{

int vcount = 0;

int opt;

while((opt = getopt( argc, argv, "v" )) != -1)

{

if(opt == 'v')

{

vcount++;

}

}

printf( "%d\n", vcount );

}

Calls the command pwd and redirect its stderr to a file named errLog

pwd 2> errLog

Permissions on the (1) directory are set so that any user can create files in it.

temp

Variable expansion but not file name expansion

" "

The (1) symbol will be expanded as the path to your current directory.

.

Old internet standard protocol for a remote terminal connection

Telnet (23)

Secure alternate protocol

ssh (22), encrypts communication between server and client

Print current time on system

date

Print the number of lines that the string "Bear" is found in the file pressRelease

grep -c "Bear" pressRelease

Print the contents of only the current directory in reverse lexicographical order

ls -r

Replace all occurrences of "Dwayne Johnson" in a file named pressRelease with "The Rock"

sed 's/Dwayne Johnson/The Rock/g' pressRelease

Vim: moves cursor to beginning of file

gg

Vim: get editor to save copy of current file

:w

Vim: get editor to move cursor to end of current line

$

Vim: undo last change to file

u

Regex that matches: catinthehat.txt

grep -E "catinthehat.txt" file_name

Regex that matches bears (first letter case insensitive)

grep -E "[Bb]ears" file_name

Regex that matches any number followed by a colon

grep -E "[0-9]+:" file_name

Regex that matches any 5 letter sequence that repeats at least once

grep -E "([a-zA-Z]{5}).*\1" file_name

Shell Expansions: files ending in .thm

*.thm

Shell Expansions: "file" followed by any single char followed by ".txt"

file?.txt

Shell Expansions: all files located in user SMITHB's home directory ending in ".sh"

~SMITHB/*.sh

Shell Expansions: files named "foo" with the first character case insensitive

[Ff]oo

Developers of UNIX

Denis Ritchie, Ken Thompson, Brian Kernighan

Current directory

.

Previous directory

..

Write to a stream (overwrite)

>

Write to a stream (append)

>>

Developers of C

Denis Ritchie, Brian Kernighan

Shell

Good for quick and simple development

KISS Principle

Keep it Small and Simple

Bash

Bourne Again Shell

sh

Bourne Shell

ksh

Korn Shell

csh

C Shell

Bash spawns new shell, executes given command, then returns result. (T/F)

True

Bash built-ins run on the original bash, and as a result, is faster and more efficient. (T/F)

True

Concatenate strings in bash

foo = "Hi"

bar = "there"

total = $foo$bar

""

Do not suppress variable expansion. Suppress shell expansion.

''

Suppress everything

``

Command substitution

- Identical to $(_)

0

Standard in

1

Standard out

2

Standard error

/dev/null

Universal trash can in Linux

kill

kills precess specified by pid

ps -ef | grep user_name

grabs all processes related to a specified user

head

returns first 10 lines

head -num

returns first num lines

tail

returns last 10 lines

tail -num

returns last num lines

Pipe

takes stdout for the first process and uses it as stdin for another process

export

allows every instance of the shell to have access to the variable

In Bash, 0 is considered true (T/F)

True

grep

global regular expression print

sed

special command (substitution in ed)

- manipulates strings, but by default, does not modify files

Remove all instances of 'TX', replace with Texas

sed 's/TX/Texas/g' file_name

sed: i

change in place

*

0 or more of the preceding pattern

? (file name expansion)

matches exactly one character

[...] (file name expansion)

character class

^

first of line

( )

capture group

$

last of line

{n, m}

range of a number of occurrences (at least n, at most m)

{n}

exactly n occurrences

{n, }

at least n occurrences

{ ,m}

at most m occurrences

+

1 or more

|

or

\

escape

* (file name expansion)

0 or more characters

?

0 or 1

Shebang line

#!/usr/bin/bash

- indicates what interprets the file

-rwxrwxrwx

Read, write, executable permissions

- 3 sets of octal numbers

- chmod

You must give file executable permissions OR (1)

1. explicitly give it bash when executing

ex. $bash ./hw.sh