UNIX for Advanced & Expert Users

dn:adcfgeneral
id:13343
Name:xxxxxx
Password:iutyerwuitywue wpuwt
tuiytruityrutyrwtyrwp
dn:cdferwjyyyy[/COLOR]
id:3875
Name:yyyy
Password :hgfdsjkfhdsfkdlshf
dshfkldshfdklsfh
interset:uiuiufj

dn:adcfgeneral|id:13343|Name:xxxxxx|Password:iutyerwuitywue wpuwttuiytruityrutyrwtyrwp
dn:cdferwjyyyy|id:3875|Name:yyyy|Password :hgfdsjkfhdsfkdlshfdshfkldshfdklsfh|interset:uiuiufj

awk '
/^dn:/ {printf("%s%s", (NR > 1) ? "\n" : "", $0)
	next
}
{	printf("%s%s", (sub(/:/, "&")) ? "|" : "", $0)
}
END {	print ""
}' file

dn:adcfgeneral|id:13343|Name:xxxxxx|Password:iutyerwuitywue wpuwttuiytruityrutyrwtyrwp
dn:cdferwjyyyy[/COLOR]|id:3875|Name:yyyy|Password :hgfdsjkfhdsfkdlshfdshfkldshfdklsfh|interset:uiuiufj

awk '($0 ~ /^dn:/ && A){print A;A="";} {A=A?A OFS $0:$0} END{print A}' OFS="|"   Input_file

dn:adcfgeneral|id:13343|Name:xxxxxx|Password:iutyerwuitywue wpuwt|tuiytruityrutyrwtyrwp
dn:cdferwjyyyy[/COLOR]|id:3875|Name:yyyy|Password :hgfdsjkfhdsfkdlshf|dshfkldshfdklsfh|interset:uiuiufj

awk '
/^dn:/ {# For input lines starting with "dn:":
	# if this is not the 1st input line, add a newline to previous output;
	# then, in either case, add the current input line (without the
	# terminating newline character) as the start of a new output line.
	printf("%s%s", (NR > 1) ? "\n" : "", $0)
	# Skip to next input line.
	next
}
{	# For other input lines:
	# If the line contains a colon, add "|" as a field separator and add the
	# current input line (withut the terminating newline character) to the
	# current output line; otherwise, just add the current input line
	# (without the terminating newline character) to the current output
	# line.
	printf("%s%s", (sub(/:/, "&")) ? "|" : "", $0)
}
END {	# When we hit EOF on the input file, add a trailing newline to the last
	# output line.
	print ""
}' file

awk '($0 ~ /^dn:/ && A){        ######## Checking here if any line is getting started with string "dn:" AND variable A is NOT NULL values in it. Where variable A is the one where I am storing all the lines values in it.
print A;                        ######## print the value of variable A then.
A="";}                          ######## Nullify the variable A's value now.
{A=A?A OFS $0:$0}               ######## Here each line I am appending the value of A with the current line's value in it.
END{print A}'                   ######## END is a awk's default section where we will perform the tasks which want to perform at last, so I am printing variable A's value here too.
OFS="|" Input_file              ######## Setting up output field separator's value to | here as per your requirement. Mentioning the Input_file name too.