• Question 1.C, 1.D • Question 5 • Quiz • Preview of HW3 • Introduction to UnixQuiz • Write an MIPS assembly program that computes the factorial of a given input. The integer input is passed through register $a0, and the result is returned in register $v0. • Show the contents of the stack after each function calls, assuming that the input is 4.Why Bother? • Most programmers who learn UNIX end up finding it useful • Provides powerful command-line interface – Many simple tasks are easier to accomplish – Possible to script repetitive operations • Widely used in research and industry, and runs most of the servers on the InternetUNIX Philosophy • Multiuser / multitasking • Toolbox approach – Combine multiple simple commands instead of using a single complex application • Designed by programmers for programmersShelling into CSUG • From Windows, use PuTTY http://www.chiark.greenend.org.uk/~sgtatham/putty/ (Google can give you this URL) – Demo • From MacOS, open a terminal and type – ssh [email protected] Line Environment • Shell is the command line interpreter – Just another program – Bourne shell (bash) – C Shell (csh) • Default shell in CSUG is tcsh • This talk uses bash – Switch to bash: exec bashRunning Commands • Commands follow the form: – command <options> <arguments> – Options modify the command – Arguments indicate what file to operate on • Get help by typing man command • Example: [msiegen@tiger ~]$ ls -l /usr total 301 drwxr-xr-x 2 root root 69632 Oct 18 08:43 bin/ drwxr-xr-x 2 root root 4096 Aug 12 2004 etc/ drwxr-xr-x 2 root root 4096 Aug 12 2004 games/ drwxr-xr-x 117 root root 20480 Sep 12 20:40 include/ ...Plumbing • I/O Redirection > Redirect standard output to file >> Append standard output to file < Get input from file • Pipes (|) are used to take the output of one program and use it as input to another e.g. du -sk /home/* | sort -nr | head -10 > disk_hogs.txtPractical Tips • Use less to view output that will not fit on your screen e.g. ls -lR | less • Use grep to filter output, and wc to count lines e.g. ps aux | grep “vim” | wc -l • Use && to run multiple commands in sequence e.g. ./configure && make && make install • Many more possibilities!File System /bin etc lib usr dev tmp home sh ls cat passwd group libc.so bin man local cs316 ttya null egs msiegen kwalsh bin mail stuffFile System • Case sensitive! • Moving around, working with directories cd Change working directory pwd Print working directory ls -la List all files in working directory mkdir Make directory rmdir Remove directory cp Copy file mv Move or rename file rm Delete a file • Searching e.g. find -name MakefileSetting Up for HW1 • Copy the HW1 files into your home directory: cp –R /usr/local/cs316/hw1_codeExamples ~ • Fix your path: export PATH=\ $PATH:/usr/local/cs316/mipsel-linux/bin • Demo compiling hw1.s and hw2.sViewing File Contents • Use cat or less: $ cat hw1.c # use cat for short files #include “test-include.h” _start() { } $ less hw1.s # use less for long filesComparing Files • Use diff: $ cat file1 Hello! This is the contents of file1. Goodbye. $ cat file2 Hello! This is the contents of file2. Goodbye. $ diff –u file1 file2 --- file1 2007-10-11 04:25:28.000000000 -0400 +++ file2 2007-10-11 04:25:45.000000000 -0400 @@ -1,3 +1,3 @@ Hello! -This is the contents of file1. +This is the contents of file2. Goodbye. • Demo: diff –u hw1.s hw2.sTransferring Files • Use WinSCP http://winscp.net/Further Reading • Manual (man) pages • OʼReilly Books – Free access on campus: http://proquest.safaribooksonline.com/ – Or from home through the Safari Tech Books link at: http://www.englib.cornell.edu/erg/shortlist.phpPlumbing • Running multiple commands in sequence – Use semicolon (;) to run commands unconditionally – Use double ampersand (&&) to run commands only until the first error occurs • Use parentheses to group a sequence and redirect output e.g. (date && ls) > logfile Not the same as: date && ls > logfileWildcards • Shorthand for referencing multiple existing files on the command line – * any number of characters – ? exactly one character – [abc] any one of a, b, or c – [!abc] any character except a, b, or c • Examples ls -l *.c lpr [Mm]akefileFile System Permissions • Permissions can be specified for – Owner – Group – All • Permissions are – Read – Write – Execute • Example: -rwxr-xr-x 1 msiegen ta 10152 Sep 21 17:04 disassemble -rw-r----- 1 msiegen ta 329 Sep 21 17:04 main.c The disassembler may be executed by anyone on the system, but the source file may only be read by people in the ta group. Both files may only be edited by the user msiegen.File System Permissions • For a directory, “read” means being able to list its contents, “execute” means being able to access files within the directory – Unless the files have more restrictive permissions • Use chmod to add or remove permissions (rwx) for user, group, and others (ugo): chmod ugo+x Let anyone execute chmod go-w Prevent non-owner form writing • Or, specify absolute permissions in octal – 4=r, 2=w, 1=x – e.g. 755=rwxr-xr-x, 640=rw-r----- e.g. chmod 755 filenameJob Control • Use & after a command to place job in background • Manage jobs: – jobs List jobs – fg %1 Bring job 1 to foreground – bg %2 Run job 2 in background – kill %3 Terminate job 3 – ^Z (control+Z) suspend foreground job – ^C (control+C) terminate foreground jobJob Control • Example [msiegen@tiger ~]$ sleep 800 & [1] 16139 [msiegen@tiger ~]$ sleep 400 & [2] 16141 [msiegen@tiger ~]$ jobs [1]- Running sleep 800 & [2]+ Running sleep 400 & [msiegen@tiger ~]$ kill %1 [msiegen@tiger ~]$ jobs [1]- Terminated sleep 800 [2]+ Running sleep 400 & [msiegen@tiger ~]$ fg %2 sleep 400 ^Z [2]+ Stopped sleep 400 [msiegen@tiger ~]$ bg %2 [2]+ sleep 400 &Environment Variables • Display all variables by typing env • Set a variable,
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