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CPS 393 Introduction to Unix and C

CPS 393 Introduction to Unix and C. START OF WEEK 2 (UNIX). 8/21/2014. Course material created by D. Woit. 1. Glob Constructs (Metacharacters) and other Special Characters. ? * [ ] #constructs saves typing, time encourages good naming conventions

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CPS 393 Introduction to Unix and C

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  1. CPS 393Introduction to Unix and C START OF WEEK 2 (UNIX) 8/21/2014 Course material created by D. Woit Course material created by D. Woit 1

  2. Glob Constructs (Metacharacters) and other Special Characters • ? * [ ] #constructs • saves typing, time • encourages good naming conventions • when shell sees a glob construct, it first *expands* word containing construct, then does command. • ? any single character • * any string of characters (incl. null string) • [...] any single char of series of chars within the brackets • e.g., assume /home/dwoit has 7 files: • lab1.jav lb2.jav new.c pie.c prog1.c prog2.c top.c • /home/dwoit> ls *.c • new.c pie.c prog1.c prog2.c top.c 8/21/2014 Course material created by D. Woit Course material created by D. Woit 2

  3. (Metacharacters) and other Special Characters cont. • /home/dwoit> ls * lab1.jav lb2.jav new.c pie.c prog1.c prog2.c top.c • /home/dwoit> ls prog?.c prog1.c prog2.c • /home/dwoit> ls p*.c prog1.c prog2.c pie.c • /home/dwoit> ls ???.* lb2.jav new.c pie.c top.c • /home/dwoit> ls prog[123].c prog1.c prog2.c 8/21/2014 Course material created by D. Woit Course material created by D. Woit 3

  4. Metacharacters and other Special Chars cont. • /home/dwoit> ls [m-s]* # all files starting with m ... s new.c pie.c prog1.c prog2.c • [1-5A-Z] matches any char 1,2,3,4,5,A,B,C, ... Z • [!ABC] matches any char *except* A, B or C • [!a-z0-47] matches any char *except* a,b,c, ... z, 0,1,2,3,4,7 • NOTE: ranges, such as a-z depend on locale having LC_COLLATE set normally. • It can be set to something weird, such as thinking order is aAbBcC...zZ instead of the normal ASCII sequence abc..zABC...Z • You can do a simple test to check it out: e.g., if ls [a-z] matches A it is not normal. (in latest bash, either ! or ^ is not) 8/21/2014 Course material created by D. Woit Course material created by D. Woit 4

  5. Other special characters, expanded to • ~ your home directory name (e.g. /home/dwoit ) • from any dir, ls ~ lists your home dir (/home/jmisic for me) • cd ~/cps393 changes into dir /home/jmisic/cps393 for me • ~usr the home dir of user with userid "usr " • ~- your previous working dir (note in bash cd - == cd ~-) • ~+ your current working dir • Example: toggle between 2 dirs with "cd -" in bash • /home/dwoit> cd bin • /home/dwoit/bin> cd - • /home/dwoit> cd - • /home/dwoit/bin> 8/21/2014 Course material created by D. Woit Course material created by D. Woit 5

  6. Directories and files • /home/jmisic/cps393> echo my working dir is ~+ • my working dir is /home/jmisic/cps393 • /home/jmisic/cps393/labs> echo all the files in this dir are * • all the files in this dir are lab1.txt • However, if we put the quotes we get: • /home/jmisic/cps393/labs> echo “all the files in this dir are *” • echo all the files in this dir are * • /home/jmisic/cps393/labs> echo all the files in this dir are “*” • echo all the files in this dir are * 8/21/2014 Course material created by D. Woit Course material created by D. Woit 6

  7. Directories and files cont. • Special chars are not expanded if within single or double quotes • escape character \ before any special char works like quotes • /home/jmisic/cps393/labs> echo all the files in this dir are \* • echo all the files in this dir are * 8/21/2014 Course material created by D. Woit Course material created by D. Woit 7

  8. Patterns and Regular Expressions in Shell • in ksh they work normally • -in bash if you execute first: shopt -s extglob (extended pattern matching) • Without this option only *, ? And […] work. • For example: • *(exp) 0 or more occurrences of exp • +(exp) 1 or more occurrences of exp • ?(exp) 0 or 1 occurrences of exp • @(exp1|exp2|...) exp1 or exp2 or ... • !(exp) anything that doesn't match exp 8/21/2014 Course material created by D. Woit Course material created by D. Woit 8

  9. Patterns and Regular Expressions in Shell • Example: if you had files in the current dir such as below: • A Ax Axxx Axxxx X X.bak x xx xxxx • Then (but carefully since no extra spaces are allowed in braces): • shopt -s extglob • ls A*(x) prints A Ax Axxx Axxxx • ls A*(xx) prints A Axxxx • ls A+(x) prints Ax Axxx Axxxx • ls A?(x) prints A Ax • ls X?(.bak) prints X X.bak • ls @(*xx|*ak) prints Axxx Axxxx X.bak xx xxxx • ls !(@(*xx|*ak)) prints A Ax X x 8/21/2014 Course material created by D. Woit Course material created by D. Woit 9

  10. Homework • How would you list all file/dir names that: • 1. contained the letter "e"; • 2. had a total of 7 letters and no extension; • 2a. are 7 characters long; • 3. had 3 letter extensions; • 3a. had 3 letter alpha-numeric extensions; • 4. contained the word "tst" *somewhere* inthe name; • 5. started with the letter "A" and contained a dash (-); • 6. are at least 2 characters long and don't have the following letters anywhere in the first 2 characters: a,b,c,f,h,x,y,z • 7. end in .ex with an optional c at the end • 8. are not java or text files (don't end in .jav or .txt) • 9. end in a : followed by a digit from 2-8 followed zero or more digits. 8/21/2014 Course material created by D. Woit Course material created by D. Woit 10

  11. Interactive Shell Use • Is usually used for • typing on command line • one-time task • Prototyping • For repetitive use we build Shell scripts (Shell programs) • task complex • repeat it later 8/21/2014 Course material created by D. Woit Course material created by D. Woit 11

  12. Example shell script • #!/bin/bash • #source: showSource • #shell program to list all source java and c files in current directory • echo -n "Current directory is: " • pwd • echo "C files are:" • ls *.c • echo "Java files are:" • ls *.jav • To run:make sure it is executable (chmod ugo+x showSource or chmod +x showSource ), then • jmisic@metis:~/cps393/labs$ ./showSource 8/21/2014 Course material created by D. Woit Course material created by D. Woit 12

  13. Example output of the script is: • jmisic@metis:~/cps393/labs$ ./showSource • current directory is/home/jmisic/cps393/labs • c files are: • smitz5.c smitz_scanf.c • java files are: • proba.jav Course material created by D. Woit

  14. Arguments to shell script: $1 $2 $3 etc. • $0 name of shell pgm • $# count of # of args passed • $@ lists args as one string: "arg1 arg2 ...“ • $* lists args as separate : "arg1" "arg2" ... • Example: • #!/bin/bash • #source: prnargs • #shell pgm to print out its first 2 args • echo The first argument is: $1 • echo The second argument is: $2 • exit 0 Course material created by D. Woit

  15. Arguments: $1 $2 $3 etc. • To run set execute permissions: • jmisic@metis:~/cps393/labs$ ./prnargs "Hello there " world • The first argument is: Hello there • The second argument is: world • Note: • could have used quotes in echo: • echo "The first argument is: " $1 • echo "The second argument is:" $2 • or could have used echo backslash-escape TAB char, \t (see man echo) • echo -e "The first argument is:\t" $1 • echo -e "The second argument is:\t" $2 Course material created by D. Woit

  16. How to leave out the ./ • current dir has to be in your path • If you wish to invoke prnargs (instead of ./prnargs ) • you need to edit your .profile file in your home directory (but save it first) • Since current directory is represented as null name followed by a colon you have to insert at the end : • PATH=$PATH:: • export PATH • Export command makes PATH variable available to all subsequent processes initiated by the user. Course material created by D. Woit

  17. Filters • Filter refines or transforms the input to produce (usually different) output • stdin -------> filter --------> stdout • E.g. more < file1 • transforms sequence of characters from file1 (its input) • into the same sequence but with pagination Course material created by D. Woit

  18. Grep (globally look for a regular expression and print) • grep string filename(s) • string: the string to search for • filename(s): one or more files to search in • result: displays lines of file(s) filename(s) that contain the given string • (precisely: sends to stdout lines of stdin that contain string) • e.g. grep 'applet' lab1.jav lab2.jav • sends to stdout (screen) those lines of files lab1.jav and • lab2.jav that contain the string applet • /home/jchan> grep 'applet' lab1.jav lab2.jav • lab1.jav: applet.init(); • lab1.jav: applet.start(); • lab2.jav: applet.num=6; Course material created by D. Woit

  19. Grep cont. • e.g. You forgot the exact syntax for 'for' construct in java. • You know it is used in one of your .jav files. Do: • grep 'for' *.jav • to get a list of all files/lines containing for • Then edit or more one file to see exact syntax • Note: • single quotes are good for now. Once we study variables, you • we will have reason to use double quotes around the search string. • Options for grep • -i option: ignore case of search string • -v option: print lines *not* matching search string Course material created by D. Woit

  20. Grep with regular expressions and metacharacters • . any character, except newline (like ? in glob) • * 0 or more repetitions of previous character (not like glob!) • ^ beginning of line • $ end of line • [ ... ] any character inside the brackets (like glob) • [^ ... ] any character *not* inside the brackets (like ! or ^ in glob) • [! ... ] same as above on some implementations • \{m\} exactly m repetitions of previous character • \{m,n\} any number of repetitions of prev char between m and n inclusive • \< beginning of word • \> end of word • remember to quote these as in: grep '\<a_word\>' a_file Course material created by D. Woit

  21. Examples: Grep with special chars. • grep '^Assignment' fname # lines starting with Assignment • grep -v '^Assignment' fname # lines not starting with Assignment • grep 'Assignment$' fname # lines ending with Assignment • grep 'd.g' fname # lines containing dag, dbg, dcg, d0g, d1g, etc • grep 'su*m' fname # lines containing sm, sum, suum, suuum, etc. • grep '\<so\>' fname # *word* so (vs. social, absolute) • grep '[A-Za-z][A-Za-z]*' fname # lines containing ANY non-empty alpha string (no blank lines, lines with digits, etc) Course material created by D. Woit

  22. Examples: Grep with special chars • grep 'xyz\.[^ ]* ' # lines containing string xyz followed by a dot followed by 0 or more non-spaces, then one space e.g., "xyz. " "xyz.w " "xyz.ta " etc (see slide 20) • grep 'xyz\.w\{2,3\}X' # lines containing xyz.wwX or xyz.wwwX Course material created by D. Woit

  23. Grep with Extended Regular Expressions: • use grep -E or egrep (system dependent) OR • + 1 or more repetitions of previous character • e.g., • grep -E 'dog|cat|bird' fname # lines with at least 1 of dog, cat, or bird • grep -E '[A-Za-z]+' fname # lines with at least one alpha char • Note this also matches lines with no alpha chars since * matches null: • grep '[A-Za-z]*' fname Course material created by D. Woit

  24. Homework • In the shell, is grep '[A-Za-z][A-Za-z]*' fname the same as grep -i '[A-Z]*' fname ? Why or why not? • Why do you think "\<" and \>" are used instead of simply "<" and ">" for beginning/end of line? • For questions 1-6 below, write a different shell program. • list all lines in file fname containing the string "dog"; • list all lines in fname containing the word "dog"; • list all lines in fname containing the string "dog" at the beginning of a line; • list all lines in fname containing the word "dog" at the beginning of a line. • list all lines in fname containing exactly 6 "a"s in a row. • list all lines in fname containing one or more words that start with 93 and end in a sequence of any number of W (not 0) • Find 3 different grep commands that will list lines of fname that end in a vowel. • Use the man page to find the option of grep that shows the matched string in a different color. Try it. Course material created by D. Woit

  25. find (list all files and dirs meeting certaincriteria ) • e.g., this lists all java files in portion of the file system rooted at /home/dwoit: • find/home/dwoit-name "*.jav" • match any file with name *.jav (glob) • dir to search (this dir and all its subdirectories ) • find.-type f# lists all *files* in filesystem rooted at the current dir (.) (i.e., no directories listed; for dirs -type d) Course material created by D. Woit

  26. find cont. • find/usr-name banner 2>/dev/null • find.-type d -perm -g+r,u+r # all dirs rooted in current dir that are readable by both owner and group LOTS of ways to specify perms--see man find Course material created by D. Woit

  27. Notes for find • If you want it to go down symbolic links, you might have to use the -follow option. • Some versions of linux have default find commands that follow automatically, and others don't... • Some years scs students' home dirs are symbolic links. • Note: if glob constructs not in quotes, shell expands *first* and then sends all to find. Again, single or double quotes OK for now. Course material created by D. Woit

  28. HMWK • Use the "find" command to list all files in directory /bin that start with the letter "m". • What would happen if we did not put a name such as "*.jav" in quotes in the find command? Make sure you have some .jav files in your directory and try it out. • Look at the man pages for "find" to determine what the option "-mtime" does in the find command. Then..Figure out a sequence of commands (involving a find, temp file and a grep) to display those files in the current directory whose contents werechanged within the last 24 hours and whose names contain the string "tst". • Make a shell program to do question 3 above. Call your program tstRecent. Your program should delete any temporary files it creates.Test it to make sure your program works. • Use the man pages to find out how find's -maxdepth option works. Use -maxdepth 1 to list all files in the given directory only (not the whole filetree) Course material created by D. Woit

  29. Head, Tail • head sends to stdout the first 10 lines of stdin • tail sends to stdout the last 10 lines of stdin • e.g., • head<myfile # displays first 10 lines of file • myfile on screen • tail<myfile >end.of.myfile # puts copy of last 10 lines of • myfile into file called end.of.myfile • option -number displays first/last "number" lines • e.g., head -20 f1 # first 20 lines of file f1 • (options are in man pages. Lots for tail. ) Course material created by D. Woit

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