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Wiki MarkupSurviving the Shell Outline \-What is the shell? \*An interface for running programs and interacting with the OS and File System. \*5 common shells: borne (sh), bourne-again (bash), korn (ksh), c-shell (csh), and tsch \*default on Clear is tsch, default on sugar is bash (differences are mostly mini-language, such as setenv vs export for setting environment variable) \-Environment variables \*simply variable that hold strings \*this variables are inherited by programs run in the shell \*to access the value of the environment variable in the shell, prepend the name with a $ \*the PATH variable tells the shell where to look for commands typed into the shell, ':' delimit different directories. We modify it so the hjc and hj commands can be found. \*JAVA_HOME is needed so that the java compiler and jvm know where the needed libraries are located \*HJ_HOME is set for the same reason but for the HJ compiler and subsystem \*each shell inherits several environment variables on start, use the printenv command to see them \-Paths \*absolute paths begin with '/' (called root, akin to C:\\) \*relative paths don't have a starting '/' and are resolved relative to your current directory \*'.' is a special directory name for the current directory \*'..' is a special directory name for the parent directory \*spaces need to be escaped by backslash or the whole path wrapped in quotes \*tab will autocomplete directory or file names up to the first conflict \-Common Shell Commands 1. cd <dir> - change directory, takes a path 2. mv <src> <dest> - moves a file from src to dest, \-R will move a folder 3. cp <src> <dest> - like move, but copies 4. ps - see current processes running, suspended, or terminated (but not yet harvested) 5. rm <fileOrDirName> - remove file, \-R for directories. BE CAREFUL, there is no recovering what you delete. If you use the \-f flag, rm will not ask confirmation about deleting each file. rm \-Rf / will wipe the computer (hopefully you don't have permissions to do that) 6. mkdir <dirname> - creates a directory of the name given 7. chmod &nbsp;\[args\] <filename>\- changes permissions 8. touch <filename> - changes modification and access times if the file already exists, creates a new file otherwise 9. ls - list contents of current directory 10. pwd - display path to working directory (current directory) 11. echo <string> - prints the string to the screen. 12. cat <filename> - prints the contents of file to the screen 13. grep <string> <filename> - prints the lines in file that contain the string 14. printenv - prints out all the environment variables and their values \*%>man <cmdname> will display info regarding the specified command \-.Xrc Files \*a shell script that is executed before the first shell prompt is presented to you \*each shell has a .<shellname>rc file for itself, which is located in your home folder \*ideal place to do setups (like setting up HJ_HOME, JAVA_HOME, and PATH) so they are always ready on start \-vim Text Editor \*usage vim <filename> to open a file, without filename it reads from stdin \*when you open a file with vim, you open it in command mode, which means your keys do something OTHER THAN TYPING THEIR VALUES, so don't do anything until you read the next bit. \*the arrow keys move the cursor around \*the keys h,j,k,l also move the cursor around \*dd will delete the current line \*a will change to append mode, and let you type after the cursor, press escape to exit append mode \*i will change to insert mode, and let you type at the cursor, escape to exit \*in command mode, you can type : for a few other commands and press enter to execute them \*w will write your changes to your file without exiting vim \*w <filename> will write to the specified file name overwriting it if it exists, or creating it if it doesn't. \*q will quit if no changes haven't been saved. \*q\! will quit and discard unsaved changed. \*typically to exit you'll use either :wq to save and quit, or :q\! to discard your changes. \*pressing escape will exit you out of colon commands \*There are A TON of other commands to look up \-SSH and SFTP \*ssh stands for Secure Shell \*basically used for remote login \*login format is %>ssh <username>@<address> \*typical usage is <netid>@crystal.clear.rice.edu \*you'll prompted for password then, just use your netID password (except for Sugar) \*sftp stands for SSH File Transfer Protocol \*typical commands are same as a shell, but are executed on the remote machine \*prepend commands with an 'l' to execute on the local machine (ex. cd changes directory of remote machine, lcd changes local directory) \*you cannot execute programs in sftp \*%>put <src file> <dest file> copies the file from local to remote, renaming it if you specify a name different than the original \*%>get <src file> <dest file> is put's inverse, copies from remote to local \*the mput and mget variants will do their respective functions for multiple files.&nbsp; \*Typically you'll specify a regular expression (well a subset anyway) instead of the file name. \*%>mget * will get all files in the current directory of the remote machine.&nbsp; \*%>mput \*.hj will put all files ending in .hj in the local machine's current directory to the remote machine's current directory \*quit, bye, or exit will log you out of ssh and sftp \-Signals \*ctrl-C will interrupt the current running program, and get you back to the shell \*ctrl-D sends EOF \-IO Redirection \* <cmd> < <filename> operator redirects stdin from the command line to file \* <cmd> > <filename> operator redirects stdout from the command line to file \* <cmd1> \| <cmd2> 'pipe' operator redirects output of cmd1 as input to cmd2 \*the operators can be combined \-What is the shell?

• An interface for running programs and interacting with the OS and File System.
• 5 common shells: borne (sh), bourne-again (bash), korn (ksh), c-shell (csh), and tsch
• default on Clear is tsch, default on sugar is bash (differences are mostly mini-language, such as setenv vs export for setting environment variable)

...

• absolute paths begin with '/' (called root, akin to C:
  )
• relative paths don't have a starting '/' and are resolved relative to your current directory
• '.' is a special directory name for the current directory
• '..' is a special directory name for the parent directory
• spaces need to be escaped by backslash or the whole path wrapped in quotes, otherwise the path is interpreted as separate arguments delimited by the spaces
• tab will autocomplete directory or file names up to the first conflict

...

1. cd <dir> - change directory, takes a path
2. mv <src> <dest> - moves a file from src to dest, -R will move a folder
3. cp <src> <dest> - like move, but copies
4. ps - see current processes running, suspended, or terminated (but not yet harvested)
5. rm <fileOrDirName> - remove file, -R for directories. BE CAREFUL, there is no recovering what you delete. If you use the -f flag, rm will not ask confirmation about deleting each file. rm -Rf / will wipe the computer (hopefully you don't have permissions to do that)
6. mkdir <dirname> - creates a directory of the name given
7. Wiki Markup*chmod* &nbsp;\chmod  [args\] <filename>\- changes permissions
8. touch <filename> - changes modification and access times if the file already exists, creates a new file otherwise
9. ls - list contents of current directory
10. pwd - display path to working directory (current directory)
11. echo <string> - prints the string to the screen.
12. cat <filename> - prints the contents of file to the screen
13. grep <string> <filename> - prints the lines in file that contain the string
14. printenv - prints out all the environment variables and their values
15. man <cmdname> will display info regarding the specified command

...

• ctrl-C will interrupt the current running program, and get you back to the shell
• ctrl-D sends EOF

-IO Redirection

• <cmd> < <filename> operator redirects stdin from the command line to file
• <cmd> > <filename> operator redirects stdout from the command line to file
• <cmd1> | <cmd2> 'pipe' operator redirects output of cmd1 as input to cmd2
• the operators can be combined