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Full Discussion: Post Shell programming: Question about source a file and read data from the file
Top Forums Shell Programming and Scripting Post Shell programming: Question about source a file and read data from the file Post 302130302 by ccwq on Saturday 4th of August 2007 10:25:51 PM
Old 08-04-2007
Frequently Asked Questions for Assgn 3.
What does the .std_dbrc file contain?
Something like:

STD_DBROOT=${HOME}/class/2031/Assgn3/STD_DB

You do not submit this file, I will be using mine that will point to my std_db. But it should work with such a file, otherwise your program will not pass the tests.
Do we need the trailing slash (/) in the STD_DBROOT definition?
Your program should work even if there is no trailing slash. The idea is that two or more slashes are equivalent to one, so it is better if you have two slashes rather than none (disaster).
Can we invoke one of our scripts from within another script?
In principle yes, but it is far safer if you do not unless you know what you are doing. If I were you I would opt for cut and paste.
How do I use the .std_dbrc from within my own script?
You source it. Sourcing is normally just a dot (.).

. ${HOME}/.std_dbrc

If you create this file and it seems lost use

ls -a

Why can't I see my .std_dbrc with ls?
Because files that start with a dot are hidden in Unix/Linux. Use ls -a to see all your files in the current directory. I mostly use ls -ltr or ls -latr, to see the most recent (and thus most relevant files) last (the first one might have scrolled above the screen).
What does it mean to "source" a file?
The manual says:

. filename [arguments]
source filename [arguments]
Read and execute commands from filename in the current shell
environment and return the exit status of the last command exe-
cuted from filename. If filename does not contain a slash,
file names in PATH are used to find the directory containing
filename. The file searched for in PATH need not be exe-
cutable. When bash is not in posix mode, the current directory
is searched if no file is found in PATH. If the sourcepath
option to the shopt builtin command is turned off, the PATH is
not searched. If any arguments are supplied, they become the
positional parameters when filename is executed. Otherwise the
positional parameters are unchanged. The return status is the
status of the last command exited within the script (0 if no
commands are executed), and false if filename is not found or
cannot be read.

most of the details there are irrelevant to you, but the thing to keep in mind is that it executes commands from filename in the current shell environment.
Do I need to change the PATH environment variable for this assignment?
NO! You should not change the PATH. In general we do not play with PATH unless we know what we are doing.
 

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LEARN ABOUT HPUX

sh

sh(1)							      General Commands Manual							     sh(1)

NAME

       sh - overview of various system shells

SYNOPSIS

   POSIX Shell
       option] ...  string] [arg ...]

       option] ...  string] [arg ...]

   Korn Shell
       option] ...  string] [arg ...]

       option] ...  string] [arg ...]

   C Shell
       [command_file] [argument_list ...]

   Key Shell
DESCRIPTION

   Remarks
       The POSIX .2 standard requires that, on a POSIX-compliant system, executing the command activates the POSIX shell (located in file on HP-UX
       systems), and executing the command produces an on-line manual entry that displays the syntax of the POSIX shell command-line.

       However, the command has historically been associated with the conventional Bourne shell, which could confuse some users.   To  meet  stan-
       dards  requirements  and also clarify the relationships of the various shells and where they reside on the system, this entry provides com-
       mand-line syntax and a brief description of each shell, and lists the names of the manual entries where each shell is described in  greater
       detail.

       The Bourne shell is removed from the system starting with HP-UX 11i Version 1.5.  Please use the POSIX shell as an alternative.

   Shell Descriptions
       The HP-UX operating system supports the following shells:

	      POSIX-conforming command programming language and command interpreter
			residing  in  file Can execute commands read from a terminal or a file.  This shell conforms to current POSIX standards in
			effect at the time the HP-UX system release was introduced, and is similar to the Korn shell in many respects.	Similar in
			many  respects to the Korn shell, the POSIX shell contains a history mechanism, supports job control, and provides various
			other useful features.

	      Korn-shell command programming language and commands interpreter
			residing in file Can execute commands read from a terminal or a file.  This shell, like the POSIX shell, contains  a  his-
			tory mechanism, supports job control, and provides various other useful features.

	      A command language interpreter
			that incorporates a command history buffer, C-language-like syntax, and job control facilities.

	      Restricted version of the POSIX shell command interpreter.
			Sets  up  a  login  name  and  execution  environment whose capabilities are more controlled (restricted) than normal user
			shells.

	      restricted version of the Korn-shell command interpreter
			Sets up a login name and execution environment whose capabilities  are	more  controlled  (restricted)	than  normal  user
			shells.

	      An extension of the standard Korn Shell
			that uses hierarchical softkey menus and context-sensitive help.

							  +--------------+--------------------+
							  | To obtain:	 |  Use the command:  |
							  +--------------+--------------------+
							  | POSIX Shell  |  /usr/bin/sh ...   |
							  | Korn Shell	 |  /usr/bin/ksh ...  |
							  | C Shell	 |  /usr/bin/csh ...  |
							  | Key Shell	 |  /usr/bin/keysh    |
							  +--------------+--------------------+
       These shells can also be the default invocation, depending on the entry in the file.  See also chsh(1).

WARNINGS

       Many manual entries contain descriptions of shell behavior or describe program or application behavior similar to ``the shell'' with a ref-
       erence to ``see sh(1)''.

SEE ALSO

       For more information on the various individual shells, see:

       keysh(1)       Key Shell description.

       ksh(1)	      Korn Shell description.

       sh-posix(1)    POSIX Shell description.

       csh(1)	      C Shell description.

																	     sh(1)
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