Week 8 Lesson 8 03/21/18

Transcription

1 Week 8 Lessn 8 03/21/18 Imprtant Annuncements Extra Credits If yu haven t dne s, send yur pictures t risimms@cabrill.edu fr 3 pints EXTRA CREDIT. Jin LinkedIn fr 3 pints Perkins/VTEA Survey (check frum) fr 3 pint extra credit Class Attendance Attending class by watching the recrding in the archives? Make sure yu the instructr fr attendance First minute quizzes: 9AM Lg in credentials are yur usernames and passwrds. See instructr s welcme annuncement n CANVAS Text Bk Text bk is ptinal: Harley Hahn s Guide t Unix and Linux by Harley Hahn, McGraw- Hill ISBN: Exams (see calendar) FINAL EXAM WILL BE ON WEDNESDAY, MAY 23 FROM 7:00 AM-9:50 Frum USE FORUM if needed help (remember extra psts in ne quarter d nt carry ver t the next quarter) Time zne Class uses Opus-ii time. Fr mre inf, ask n frum. Grade Keep track f yur grade Netwrking Subscribe t Cabrill Netwrking Prgram Mailing list. Send t netwrkerssubscribe@cabrill.edu File Permissins New Cmmands - find find file r cntent f a file - grep Glbal Regular Expressin Print - srt srt - spell spelling crrectin - wc wrd cunt - tee split utput - cut cut fields frm a line

2 srt <ptins> <filepath> a. the srt cmmand can read lines frm a file r stdin and srt them. The -r ptin will d a reverse srt. i. /hme/cis90/simben $ srt names (ne argument which is a filename) The srt cmmand will srt the lines in a file and utput the srted lines (see slides fr examples) 1. The Prmpt string is:/hme/cis90/simben $ 2. Parsing results: cmmand:srt; n ptins; 1 argument:names n redirectin 3. Search user s path and lcate the srt prgram in /bin 4. Srt laded int memry and executin begins 5. After execute the srt utput either g t stdut r stderr ii. /hme/cis90/simben $ srt (N argument specified)if n filename was specified, srt will read input frm the keybard. Ctrl-D specifies the EOF (End Of File). After srt receives the EOF it srts the lines and utputs them. (see slides fr examples) iii. /hme/cis90/simben $ srt bgus (n such file r directry) The srt prgram will try and pen the file it receives as an argument and print an errr message if the file des nt exist using stderr. File Descriptrs - Every prcess is given three pen files upn its executin. These pen files are inherited frm the shell. (see slides fr examples) stdin: Standard Input (0) defaults t the user s terminal keybard stdut: Standard Output (1) defaults t the user s terminal screen stderr: Standard Errr (2) defaults t the user s terminal screen File Redirectin - The input and utput f a prgram can be redirected frm and t ther files using <, >, 2> and >>: 0< r < filename redirect stdin 1> r > filename redirect stdut 2> filename redirect stderr >> filename redirect stdut and append - N arguments, redirecting stdut (see slides fr examples) [simmsben@pus ~]$ srt > dgsinrder (srt reads frm stdin and writes t stdut stdut has been redirected t the file dgsinrder) - N arguments, redirecting stdin and stdut (see slides fr examples) [simben@pus ~]$ srt < names > dgsinrder (input redirected t cme frm the file names, utput redirected t the file dgsingrder

3 Nte: The bash shell handles the cmmand line parsing and redirectin. The srt cmmand has n idea what stdin r stdut are attached t. - One argument, redirecting stdut (see slides fr examples) [simben@pus ~]$ srt names > dgsinrder (utput written t stdut is redirected t the file dgsinrder the shell, nt the srt prgram, pens the dgsinrder file). The srt prgram, nt the shell, pens and reads directly frm the names file. - One ptin, ne argument, redirecting stdut (see slides fr examples) [simben@pus ~]$ srt -r names > dgsinrder (srt writes t stdut, which is redirected t the file dgsinrder. The shell pens the dgsinrder file. The srt prcess is nt aware that utput is redirected there. -r ptin des the srt in reverse rder) Append vs Overwrite - > (verwrites) vs >> (appends) (see slide 125 fr example) [simben@pus ~]$ ech Hell Wrld >> message ( >> des nt empty file, just appends t the end. > empties then verwrites anything already in the file!) - 2> (verwrites) vs 2>> (appends) (see slide 126 fr example) /hme/cis90/simben $ ls bgus 2> errrs (2> causes the file errrs t be emptied and verwritten with errr utput) /hme/cis90/simben $ ls crud 2>> errrs (2>> appends errr utput t the errrs file) Mre redirectin examples see slides The bit bucket /dev/null - yu can thrw stuff int it and never see it again! Whatever yu redirect t /dev/null/ is gne frever /hme/cis90/simben $ ech Clean up yur rm! > /dev/null This is hw yu redirect utput t the bit bucket Pipelines: Input and Output - Cmmands may be chained tgether in such a way that the stdut f ne cmmand is piped int the stdin f a secnd prcess. Filters: A prgram that bth reads frm stdin and writes t stdut. Tees: A filter prgram that reads stdin and writes it t stdut and the file specified as the argument. - Nte: use redirectin peratrs (<, >, >>, 2>) t redirect input and utput frm and t files. Use the pipe peratr ( ) t pipe utput frm ne cmmand fr use as input t anther cmmand (see slides fr examples) [simben@pus ~]$ cat letter wc -l 28 (Cunting the lines in the letter file) cat writes t stdut which is piped t stdin fr wc! Piping is hw yu send utput frm ne cmmand fr use as input t anther cmmand.

4 find cmmand (see slides fr examples) - find <start-directry> -namne <filename>; -type <filetype>; -user<username>; - grup<grupname>; -exec <cmmand> { } \; - Use the find cmmand t find files by their name, type, wner, grup (r ther attributes) and ptinally run a cmmand n each f the files fund. - The find cmmand is recursive by default. It will start finding files at the <start directry> and includes all files and sub-directries in that branch f the file tree. - The find cmmand by itself lists all files in the current directry and recursively dwn int any sub-directries. [simben@pus pems]$ find - find cmmand the starting directry /hme/cis90/simben $ find /etc/ssh (this find cmmand will start listing files frm the /etc/ssh directry) - find cmmand -name ptin /hme/cis90/simben $ find -name 'snnet*' (since n starting directry was specified, find will start in the current directry. -name snnet* directs the find cmmand t nly lk fr files whse names start with snnet [simben@pus ~]$ find /hme/cis90 -name snnet6 2> /dev/null (all the annying errr messages are redirected t the bit bucket) [simben@pus ~]$ find / 2> /dev/null wc -l (Getting an apprximate cunt f all the files n Oput and suppressing any permissin errrs) filter cmmand (see slide 164) - A cmmand is called a filter if it can read frm stdin and write t stdut. grep cmmand (see slides fr examples) - grep <ptins> search string <filenames..> - grep -R <ptins> search string <start-directry> - use grep cmmand t search the cntents f files. Use the -R ptin t d a recursive search starting frm a directry -i (case insensitive); -w (whle wrd); -v (des nt cntain); -n (shw line number); -- clr (uses clr t shw matches) [simben@pus pems]$ grep lve Shakespeare/sn* (find the string lve in Shakespeare s snnets) [simben@pus pems]$ grep lve Shakespeare/sn* grep hate (find all lines with bth lve and hate) /hme/cis90/simben $ grep -n simben90 /etc/passwd (the -n (line number ptin) include line number it fund n) /hme/cis90/simben $ grep -i "s" pems/shakespeare/snnet[345] (lk fr s case insensitive in snnet3,4 and 5 using the -i (case insensitive) ptin) /hme/cis90/simben $ grep -w s pems/shakespeare/snnet[345] (lk fr s whle wrd nly in snnet3, 4 and 5 using the -w (whle wrd) ptin) /hme/cis90/simben $ grep -R kind. 2> /dev/null (search recursively fr files cntaining kind using the -R ptin)-

5 (see slides fr Regular Expressins examples) spell cmmand (see slides fr mre examples) - spell <filepath> - spell <filepath> <filepath> - the spell cmmand is used t check spelling f wrds in ne r mre texts files. /hme/cis90/simben/dcs $ spell magna_carta (The spell cmmand will shw any wrds nt fund in the dictinary. /hme/cis90/simben/dcs $ spell magna_carta wc -l (the -l ptin instructs the wc cmmand t just cunt the number f lines. Pipe the utput f the spell cmmand (the misspelled wrds) int the input f the wc cmmand) tee cmmand (see slides ) - tee <filepath> - The tee cmmand, a filter, reads frm stdin and writes t stdut AND t the file scpecified as the argument /hme/cis90/simben $ wh tee users srt (sends a srted list f the current users lgged n t the system t the scree, and saves an unsrted list t a file name users). cut cmmand (see slides fr examples) - cut -f <num> -d <delimiter-character> <pathname> - cut -c <start clumn>-<end clumn> <pathname> - the cut cmmand can cut text frm a line by delimited fields r by a range f clumns [rsimms@slab ~]$ grep $LOGNAME /etc/passwd cut -f 7 -d ":" (cut the 7 th field using : as the delimiter) Pipleline practice (see slides ) Permissins (see slides )