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Full Discussion: Accepting A-Za-Z
Top Forums Shell Programming and Scripting Accepting A-Za-Z Post 302462624 by DGPickett on Thursday 14th of October 2010 04:02:43 PM
Old 10-14-2010
If you want to restrict the input, this might work, except sed will want an extra linefeed:

Code:
$(
 echo 'Enter Parameter: \c' >/dev/tty
 sed '
   /[^a-zA-Z0-9]/{
      s/.*/Must contain only letters and numbers: "&"/
      w /dev/tty
      d
     }
   q
  '
 )


This is a bit busier, but you see you can do almost anything in the $() to get the parameter. narrative: Capture the stdout of a subshell as a single parameter, set output_var blank, while output_var is blank, prompt for the parameter and read one line, saving it for error output. If the line is blank or has a forbidden character, it is rejected by displaying it including expansion of any control characters and looping back else echo it out of the subshell as the parameter:

Code:
$(
   l2=""
   while [ "$l2" = "" ]
   do
    echo 'Enter Parameter: \c' >/dev/tty
    line | read l
    echo "$l" | sed '/[^a-zA-Z0-9]/d' | read l2
    if [ "$l2" = "" ]
    then
     echo "Invalid, must be only numbers and letters and not empty: '$l'" | cat -vt >/dev/tty
    fi
   done

  echo "$l2"
 )

Add " | tr '[a-z] '[A-Z]' " or
" | sed 'y/abcdefghijklmnopqrstuvwxyz/ABCDEFGHIJKLMNOPQRSTUVWXYZ/' " for all caps -- there may be other more specific options and commands, but this general solution suffices and fits other needs, too. Since there is sed in the scripts above, it can be done at the end of the current sed script parameter.
Last edited by DGPickett; 10-15-2010 at 11:13 AM.. Reason: wrong sed capitalize command
 

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LEARN ABOUT LINUX

ndd

ndd(1M) 						  System Administration Commands						   ndd(1M)

NAME

       ndd - get and set driver configuration parameters

SYNOPSIS

       ndd [-set] driver parameter [value]

DESCRIPTION

       ndd  gets  and  sets  selected configuration parameters in some kernel drivers. Currently, ndd only supports the drivers that implement the
       TCP/IP Internet protocol family.  Each driver chooses which parameters to make visible using  ndd.   Since  these  parameters  are  usually
       tightly coupled to the implementation, they are likely to change from release to release. Some parameters may be read-only.

       If the -set option is omitted, ndd queries the named driver, retrieves the value associated with the specified parameter, and prints it. If
       the -set option is given, ndd passes value, which must be specified, down to the named driver which assigns it to the named parameter.

       By convention, drivers that support ndd also support a special read-only parameter named ``?'' which can be used  to  list  the	parameters
       supported by the driver.

EXAMPLES

       Example 1: Getting Parameters Supported By The TCP Driver

       To see which parameters are supported by the TCP driver, use the following command:

       example% ndd /dev/tcp ?

       The parameter name ``?'' may need to be escaped with a backslash to prevent its being interpreted as a shell meta character.

       The following command sets the value of the parameter ip_forwarding in the dual stack IP driver to zero. This disables IPv4 packet forward-
       ing.

       example% ndd -set /dev/ip ip_forwarding 0

       Similarly, in order to disable IPv6 packet forwarding, the value of parameter ip6_forwarding

       example% ndd -set /dev/ip ip6_forwarding 0

       To view the current IPv4 forwarding table, use the following command:

       example% ndd /dev/ip ipv4_ire_status

       To view the current IPv6 forwarding table, use the following command:

       example% ndd /dev/ip ipv6_ire_status

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       nca(1), ioctl(2), attributes(5), arp(7P), ip(7P), ip6(7P), tcp(7P), udp(7P)

NOTES

       The parameters supported by each driver may change from release to release.  Like programs that read  /dev/kmem,  user  programs  or  shell
       scripts that execute ndd should be prepared for parameter names to change.

       The  ioctl()  command  that ndd uses to communicate with drivers is likely to change in a future release. User programs should avoid making
       dependencies on it.

       The meanings of many ndd parameters make sense only if you understand how the driver is implemented.

SunOS 5.10							    8 Nov 1999								   ndd(1M)
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