1. Cs288 Intensive Programming in Linux
Instructor: C F Yurkoski
Section web site:
Class 13
6-9-15

2. this weeks xkcd comic
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3. this week
Revu
Homework
Python?
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4. Revu: These are not the same: afsconnect1-57 ~ >: echo "1 2 3"
6-9-15

5. | & ; ( ) < > space tab
metacharacter
A character that, when unquoted, separates words. One of the following:
| & ; ( ) < > space tab
6-9-15

6. A token that performs a control function.
control operators
A token that performs a control function.
It is one of the following symbols:
|| & && ; ;; ( ) | |& <newline>
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7. do done elif else esac fi for function if in select then until
RESERVED WORDS
Reserved words are words that have a special meaning to the shell. The following words are recognized as reserved when unquoted and either the first word of a simple command word of a case or for command:
! case
do done elif else esac fi for
function if in select then until
while { } time [[ ]]
6-9-15

8. redirection > >>
< command < file.txt > out.txt 2> error.txt
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9. Essential commands
echo
cat
cut tr
grep
man
let ls wc
shift
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10. ECHO(1) User Commands ECHO(1)
NAME
echo - display a line of text
SYNOPSIS
echo [SHORT-OPTION]... [STRING]...
echo LONG-OPTION
DESCRIPTION
Echo the STRING(s) to standard output.
-n do not output the trailing newline
-e enable interpretation of backslash escapes
-E disable interpretation of backslash escapes (default)
--help display this help and exit
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11. If -e is in effect, the following sequences are recognized:
\\ backslash
\a alert (BEL)
\b backspace
\c produce no further output
\e escape
\f form feed
\n new line
\r carriage return
\t horizontal tab
\v vertical tab
\0NNN byte with octal value NNN (1 to 3 digits)
\xHH byte with hexadecimal value HH (1 to 2 digits)
6-9-15

12. grep, egrep, fgrep - print lines matching a pattern SYNOPSIS
GREP(1) GREP(1)
NAME
grep, egrep, fgrep - print lines matching a pattern
SYNOPSIS
grep [OPTIONS] PATTERN [FILE...]
grep [OPTIONS] [-e PATTERN | -f FILE] [FILE...]
DESCRIPTION
grep searches the named input FILEs (or standard input if no files are
named, or if a single hyphen-minus (-) is given as file name) for lines
containing a match to the given PATTERN. By default, grep prints the
matching lines.
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13. Divide a file into several parts (columns)
cut
Divide a file into several parts (columns)
Writes to standard output selected parts of each line of each input file, or standard input if no files are given or for a file name of `-'.
Syntax
cut [OPTION]... [FILE]...
In the options below, BYTE-LIST, CHARACTER-LIST, and FIELD-LIST are one or more numbers or ranges (two numbers separated by a dash)
Bytes, characters, and fields are are numbered starting at 1 and separated by commas.
Incomplete ranges can be given: -M means 1-M ; N- means N through end of line or last field.
6-9-15

14. 6-9-15

15. tr - translate or delete characters Synopsis
Name
tr - translate or delete characters
Synopsis
tr [OPTION]... SET1 [SET2]
Description
Translate, squeeze, and/or delete characters from standard input, writing to standard output.
-c, -C, --complement
use the complement of SET1
-d, --delete
delete characters in SET1, do not translate
-s, --squeeze-repeats
replace each input sequence of a repeated character that is listed in SET1 with a single occurrence of that character
6-9-15

16. character with octal value NNN (1 to 3 octal digits) \\ backslash \a
audible BEL \b
backspace \f
form feed \n
new line \r
return \t
horizontal tab \v
vertical tab
6-9-15

17. CAT(1) User Commands CAT(1) NAME top
cat - concatenate files and print on the standard output
SYNOPSIS top
cat [OPTION]... [FILE]...
DESCRIPTION top
Concatenate FILE(s) to standard output.
With no FILE, or when FILE is -, read standard input.
-A, --show-all
equivalent to -vET
-b, --number-nonblank
number nonempty output lines, overrides -n
-e equivalent to -vE
-E, --show-ends
display $ at end of each line
-n, --number
number all output lines
6-9-15

18. wc - print newline, word, and byte counts for each file Synopsis
Name
wc - print newline, word, and byte counts for each file
Synopsis
wc [OPTION]... [FILE]...
wc [OPTION]... --files0-from=F
Description
Print newline, word, and byte counts for each FILE, and a total line if more than one FILE is specified. With no FILE, or when FILE is -, read standard input.
-c, --bytes
print the byte counts
-m, --chars
print the character counts
-l, --lines
print the newline counts
6-9-15

19. 6-9-15 Name ls - list directory contents Synopsis
ls [OPTION]... [FILE]...
Description
List information about the FILEs (the current directory by default). Sort entries alphabetically if none of -cftuvSUX nor --sort.
Mandatory arguments to long options are mandatory for short options too.
-a, --all
do not ignore entries starting with .
-A, --almost-all
do not list implied . and ..
--author
with -l, print the author of each file
-b, --escape
print octal escapes for nongraphic characters
--block-size=SIZE
use SIZE-byte blocks. See SIZE format below
-B, --ignore-backups
do not list implied entries ending with ~ -c
with -lt: sort by, and show, ctime (time of last modification of file status information) with -l: show ctime and sort by name otherwise: sort by ctime -C
list entries by columns
--color[=WHEN]
colorize the output. WHEN defaults to 'always' or can be 'never' or 'auto'. More info below
-d, --directory
list directory entries instead of contents, and do not dereference symbolic links
-D, --dired
generate output designed for Emacs' dired mode -f
do not sort, enable -aU, disable -ls --color
-F, --classify
append indicator (one of to entries
--file-type
likewise, except do not append '*'
--format=WORD
across -x, commas -m, horizontal -x, long -l, single-column -1, verbose -l, vertical -C
--full-time
like -l --time-style=full-iso -g
like -l, but do not list owner
--group-directories-first
group directories before files.
augment with a --sort option, but any
use of --sort=none (-U) disables grouping
-G, --no-group
in a long listing, don't print group names
-h, --human-readable
with -l, print sizes in human readable format (e.g., 1K 234M 2G)
--si
likewise, but use powers of 1000 not 1024
-H, --dereference-command-line
follow symbolic links listed on the command line
--dereference-command-line-symlink-to-dir
follow each command line symbolic link that points to a directory
--hide=PATTERN
do not list implied entries matching shell PATTERN (overridden by -a or -A)
--indicator-style=WORD
Name
ls - list directory contents
Synopsis
ls [OPTION]... [FILE]...
Description
List information about the FILEs (the current directory by default). Sort entries alphabetically if none of -cftuvSUX nor --sort.
Mandatory arguments to long options are mandatory for short options too.
-a, --all
do not ignore entries starting with .
-A, --almost-all
do not list implied . and ..
--author
with -l, print the author of each file
-b, --escape
print octal escapes for nongraphic characters
--block-size=SIZE
use SIZE-byte blocks. See SIZE format below
-B, --ignore-backups
do not list implied entries ending with ~ -c
with -lt: sort by, and show, ctime (time of last modification of file status information) with -l: show ctime and sort by name otherwise: sort by ctime -C
list entries by columns
--color[=WHEN]
colorize the output. WHEN defaults to 'always' or can be 'never' or 'auto'. More info below
-d, --directory
list directory entries instead of contents, and do not dereference symbolic links
-D, --dired
generate output designed for Emacs' dired mode -f
do not sort, enable -aU, disable -ls --color
6-9-15

20. shift - shift positional parameters SYNOPSIS shift [n] DESCRIPTION
NAME
shift - shift positional parameters
SYNOPSIS
shift [n]
DESCRIPTION
The positional parameters shall be shifted. Positional parameter 1 shall be assigned the
value of parameter (1+n), parameter 2 shall be assigned the value of parameter (2+n), and
so on. The parameters represented by the numbers "$#" down to "$#-n+1" shall be unset, and
the parameter '#' is updated to reflect the new number of positional parameters.
The value n shall be an unsigned decimal integer less than or equal to the value of the
special parameter '#' . If n is not given, it shall be assumed to be 1. If n is 0, the
positional and special parameters are not changed.
6-9-15

21. pipes The format for a pipeline is:
[time [-p]] [ ! ] command [ [|│|&] command2 ... ]
e.g:
command1 | commnd2
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22. programming in bash
conditionals
loops
arrays
functions
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23. File permissions chmod and ls afsconnect1-44 ~ >: chmod 751 cfy
afsconnect1-45 ~ >: ls -ld cfy
drwxr-x--x 4 yurkowsk afs 2048 Apr 12 10:58 cfy/
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24. Variable and special variables$# $? $*
$1 - $9
$a ${a} ${a[*]}
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25. Useful cc options -c suppress linking -I add directory to include list
-o renames output file
-L add directory to library list
-v Causes the compiler to perform more and stricter semantic
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26. preprocessor
cpp
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27. linking ar ld
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28. manipulating pointers
linked lists
binary trees
stacks
heaps
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29. client/server library
socket, bind, listen, accept and friends
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30. stdio.h
fopen, fprintf, fread, etc.
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31. string library
strcmp, strcat, strcpy, etc
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32. Bit operations
& | ^ ~
>>
<<

33. #include <stdio.h>
main(){
int sum=0, j;
printf("input:\n");
while(scanf("%d",&j)!=EOF)
sum|=j;
printf("output:\n%x\n",sum); }
afsconnect1-153 ~ >: mysum
input: 3 5
output: 7

35. solution

36. cfy

37. cfy

38. Homework: server side
Write a server which accepts as command line argument a port number on the local host. It should attempt open that port. If it cannot open the port it should print the value of errno and exit.
Otherwise it should listen for incoming requests on that port.
It should write to standard output any input it receives on the socket on which it is listening.

39. int main(int argc, char *argv[]){
int sockfd, newsockfd, portno;
socklen_t clilen;
char buffer[256];
struct sockaddr_in serv_addr, cli_addr;
int n;
if (argc < 2) {
fprintf(stderr,"ERROR, no port provided\n");
exit(1); }
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = atoi(argv[1]);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno); /* host to network */
if (bind(sockfd, (struct sockaddr *) &serv_addr,
sizeof(serv_addr)) < 0)
error("ERROR on binding");

40. #include <stdio.h> main(){ int j=123;
Big-endian versus little-endian: Big-endian is an order in which the "big end" (most significant value in the sequence) I
s stored first (at the lowest storage address).
#include <stdio.h>
main(){
int j=123;
printf("%.4x %.4x\n",j,htons(j)); }
afsconnect1-129 ~ >: ./testhtons
007b 7b00

41. listen(sockfd,5);
clilen = sizeof(cli_addr);
newsockfd = accept(sockfd,(struct sockaddr *) &cli_addr,
&clilen);
if (newsockfd < 0)
error("ERROR on accept");
bzero(buffer,256);
n = read(newsockfd,buffer,255);
if (n < 0) error("ERROR reading from socket");
printf("Here is the message: %s\n",buffer);
n = write(newsockfd,"I got your message",18);
if (n < 0)
error("ERROR writing to socket");
close(newsockfd);
close(sockfd);
return 0; }

42. Homework: client side
Write a client which accepts as command line arguments the name of a server and a port on that server.
The client should attempt to open a socket to that server/port.
If it fails it should output the reason and errno.
Otherwise it should read a line from standard input and write it to the server and it the example above.

43. int main(int argc, char *argv[]){
int sockfd, portno, n;
struct sockaddr_in serv_addr;
struct hostent *server;
char buffer[256];
if (argc < 3) {
fprintf(stderr,"usage %s hostname port\n", argv[0]);
exit(0); }
portno = atoi(argv[2]);
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
server = gethostbyname(argv[1]);
if (server == NULL) {
fprintf(stderr,"ERROR, no such host\n");

44. The <netdb.h> header defines the hostent structure that includes
at least the following members:
char *h_name Official name of the host.
char **h_aliases A pointer to an array of pointers to
alternative host names, terminated by a
null pointer.
int h_addrtype Address type.
int h_length The length, in bytes, of the address.
char **h_addr_list A pointer to an array of pointers to
network addresses (in network byte order)
for the host terminated by a null pointer.

45. bzero((char *) &serv_addr,
sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr,
(char *)&serv_addr.sin_addr.s_addr,
server->h_length);
serv_addr.sin_port = htons(portno);
if (connect(sockfd,(struct sockaddr *)
&serv_addr,sizeof(serv_addr)) < 0)
error("ERROR connecting");
printf("Please enter the message: ");
bzero(buffer,256);
fgets(buffer,255,stdin);
n = write(sockfd,buffer,strlen(buffer));
if (n < 0)
error("ERROR writing to socket");
n = read(sockfd,buffer,255);
error("ERROR reading from socket");
printf("%s\n",buffer);
close(sockfd);
return 0; }

46. Bit operator exercise
Write a mysum program which read integers from standard input, exclusive ors them together and writes the resulting value in hex to standard output.
Hint use scanf to read the integers.

48. pointers
char c='a', d='b', *cp; cp= &d; *cp=c; cp++;

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

50. Preprocessor directives
#include < > versus double quotes #define #ifdef #else #endif

51. break

52. python the version of python on afs5 requires parenthesis with print

53. conditional operators
same as C with the addition of <>
tmp]$ python
Python (default, Aug , 15:58:25)
[GCC (Red Hat )] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> x=2
>>> print x == 2
True
>>> print x != 2
False
>>> print x <> 2
>>>
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54. booleans and & or instead of && and || >>> x=1
>>> y=2
>>> if x == 1 and y == 2:
print ("both true")
...
both true
>>>
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55. similarly not instead of !
>>> print (not False) True >>>
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56. >>> if x == 2 and y == 2:. print ("both true"). else:
>>> if x == 2 and y == 2: ... print ("both true") ... else: ... print ("at least one is false") ... at least one is false >>>
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57. Indentation
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58. numeric type
floats and integers:
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59. strings
single or double quotes
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60. comments
# this is a comment
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61. arithmetic operators + - * % / // (floor) ** (power) e=2.71 pi=3.14
print ( e ** pi)
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62. arrays afsconnect1-51 python >: cat array.py array = [1,2,3]
print (array[0])
print (array[1])
print (array[2])
afsconnect1-52 python >: python array.py 1 2 4
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63. lists
afsconnect1-59 python >: cat list.py list = [] list.append(1) list.append(2) list.append(3) # prints out 1,2,3 for x in list: print (x) afsconnect1-60 python >: python list.py afsconnect1-61 python >:
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64. can use multiplication operator on lists
>>> print ([1,2,3] * 3 ) [1, 2, 3, 1, 2, 3, 1, 2, 3] >>>
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65. C style format strings
>>> name="Lou Cifer" >>> grade=66.6 >>> print ("the grade for %s is %f " % (name , grade ) ) the grade for Lou Cifer is >>> print (len(name)) 9 >>> print (name.index("C")) 4 >>>
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66. import other modules
$ cat main.py import sys print (len(sys.argv)) $ python main.py 1 $ python main.py a bc def 4 $
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67. loops
import sys y=0 x=len(sys.argv) while y < x: print sys.argv[y] y += 1 $ python main.py a bc def main.py a bc def $
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68. atoi (int)
$ cat convert.py string = "1" integer = 1 print ("string and integer are not the same:"), print ( integer == string ) print ("unless converted:"), print ( integer == int(string)) $ python convert.py string and integer are not the same: False unless converted: True $
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69. reprise of homework 4, problem 3 redo with python instead of C or bash
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70. something like this:
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71. afsconnect1-55 python >: cat sort
afsconnect1-55 python >: cat sort.py # print sort and print integers in ascending order import sys array=sys.argv x=len(sys.argv) if x < 2: print ("Usage: python %s sting of integers " % sys.argv[0]) sys.exit(-1) y=1 while y < x: z=y while z < x: if int(array[y]) > int(array[z]): temp=array[y] array[y]=array[z] array[z]=temp z+=1 y+=1 z=1 while z < x : print ( array[z], end=" " ) print ("\n") afsconnect1-56 python >:
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