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Full Discussion: Unix Shell Scripting
Top Forums UNIX for Dummies Questions & Answers Unix Shell Scripting Post 302686489 by Don Cragun on Tuesday 14th of August 2012 04:57:21 PM
Old 08-14-2012
First, there are two flavors of the echo utility. The BSD-based version of echo concatenates all of the operands it is given and write them to standard output followed by a <newline>. If the -n option is present it doesn't output the <newline>. I assume this is the version of echo you have on your system. (On the UNIX System V-based version of echo -n is not an option; it is just another operand to be printed. But there are several escape sequences in the string operands that the System V echo will translate ("\t" -> <tab>, "\n" -> <newline>, "\0" -> skip the remainder of this and any following operand and skip the normal trailing <newline>, etc.) that the BSD echo will not change.) If you want to output some text without the normal trailing <newline> in a way that will be portable to all UNIX and Linux systems, use the printf utility instead of echo.

So, your cout << "string" being roughly equivalent to [icode]echo -n "string" is pretty close. But echo $1 is also an output statement; not an input statement. I'm more of a C guy, than C++. In C it is roughly equivalent to printf("%s\n", argv[1]);. The equivalence is would be exact if you used "$1" instead of $1 because if the string isn't quoted and you have the default setting for $IFS, any sequences of one or more <space> and <tab> characters will be translated to a single space and passed to the echo command as individual operands instead of as a single string.

In the shells (bash, ksh, sh, ...), $n (1 <= n <= 9) refers to the 9th argument given to to the shell script when it was invoked. If you use ${n}, n can be greater than 9. $0 refers to the name of the script (like argv[0] in a C or C++ program). So, if you have a regular file with the execute bit set named "script" that contains something like:
Code:
#!/bin/ksh
echo -n "There once was a "
echo $1
echo -n "that "
echo $2
echo -n "who liked to " 
echo $3
echo -n "There once was a " $1 " that " $2 " who liked to " $3

and invoked it as:
Code:
script man "spent a lot of time in a swimming pool" "win gold medals!"

the output should be something like:
Code:
There once was a man
 that spent a lot of time in a swimming pool
 who liked to win gold medals!
There once was a man that spent a lot of time in a swimming pool who liked to win gold medals!

 

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CPANPLUS::Shell::Default::Plugins::Source(3pm)		 Perl Programmers Reference Guide	    CPANPLUS::Shell::Default::Plugins::Source(3pm)

NAME
CPANPLUS::Shell::Default::Plugins::Source - read in CPANPLUS commands SYNOPSIS
CPAN Terminal> /source /tmp/list_of_commands /tmp/more_commands DESCRIPTION
This is a "CPANPLUS::Shell::Default" plugin that works just like your unix shells source(1) command; it reads in a file that has commands in it to execute, and then executes them. A sample file might look like this: # first, update all the source files x --update_source # find all of my modules that are on the CPAN # test them, and store the error log a ^KANE$' t * p /home/kane/cpan-autotest/log # and inform us we're good to go ! print "Autotest complete, log stored; please enter your commands!" Note how empty lines, and lines starting with a '#' are being skipped in the execution. BUG REPORTS
Please report bugs or other issues to <bug-cpanplus@rt.cpan.org<gt>. AUTHOR
This module by Jos Boumans <kane@cpan.org>. COPYRIGHT
The CPAN++ interface (of which this module is a part of) is copyright (c) 2001 - 2007, Jos Boumans <kane@cpan.org>. All rights reserved. This library is free software; you may redistribute and/or modify it under the same terms as Perl itself. SEE ALSO
CPANPLUS::Shell::Default, CPANPLUS::Shell, cpanp perl v5.18.2 2014-01-06 CPANPLUS::Shell::Default::Plugins::Source(3pm)
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