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Full Discussion: Hi im new to bash scripting I want to know what does the regex expression do ??
Top Forums Shell Programming and Scripting Hi im new to bash scripting I want to know what does the regex expression do ?? Post 302722319 by kevin298 on Friday 26th of October 2012 06:19:22 PM
Old 10-26-2012
Hi im new to bash scripting I want to know what does the regex expression do ??
# check host value regex='^([1-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(\.([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])){3}$' if [ "$(echo $host | grep '[A-Za-z]')" != "" ]; then if [[ "$(host $host)" =~ "not found" ]]; then echo host $host not found exit 4 fi elif [[ ! $host =~ $regex ]]; then echo $host is an invalid host address exit 5 fi
 

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LEARN ABOUT FREEBSD

realhostname

REALHOSTNAME(3) 					   BSD Library Functions Manual 					   REALHOSTNAME(3)

NAME

     realhostname -- convert an IP number to the real host name

LIBRARY

     System Utilities Library (libutil, -lutil)

SYNOPSIS

     #include <libutil.h>

     int
     realhostname(char *host, size_t hsize, const struct in_addr *ip);

DESCRIPTION

     The function realhostname() converts ip to the corresponding host name.  This is done by resolving ip to a host name and then ensuring that
     the host name resolves back to ip.

     host must point to a buffer of at least hsize bytes, and will always be written to by this function.

     If the name resolution does not work both ways or if the host name is longer than hsize bytes, inet_ntoa(3) is used to convert ip to an ASCII
     form.

     If the string written to host is hsize bytes long, host will not be NUL terminated.

RETURN VALUES

     The realhostname() function will return one of the following constants which are defined in <libutil.h>:

	HOSTNAME_FOUND
	     A valid host name was found.

	HOSTNAME_INCORRECTNAME
	     A host name was found, but it did not resolve back to the passed ip.  host now contains the numeric value of ip.

	HOSTNAME_INVALIDADDR
	     ip could not be resolved.	host now contains the numeric value of ip.

	HOSTNAME_INVALIDNAME
	     A host name was found, but it could not be resolved back to any ip number.  host now contains the numeric value of ip.

SEE ALSO

     gethostbyaddr(3), gethostbyname(3), inet_ntoa(3), realhostname_sa(3)

BSD
								   April 6, 1999							       BSD
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