substitution in a string

s_gaurav1091 has asked for the wisdom of the Perl Monks concerning the following question:

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Re: substitution in a string by pjf (Curate) on Sep 28, 2005 at 08:54 UTC
G'day s_gaurav1091 Trying to reduce your steps? Sounds like good old fashioned perl-golf. ;) However, I'll try to give suggestions that make your code more tidy but without loss of readability. You can reduce your `if` to testing a single regular expression. The code below uses some more specific variable names, and pushes non-oracle variables onto our output array without alteration. my @envArray = `rsh sdp1 su - oracle8 -c env `; my @translated_env; # Rather than '@array'. foreach (@envArray) { if ( m{^( ORACLE_SID \| ORACLE_HST_SID \| ORACLE_HOME \| SDP_HOME )=( +.)}ix ) { # Look, an oracle variable! my ($env_key, $env_value) = ($1, $2); # $env_key rather tha +n $temp # Tweak it... $env_key = lc($env_key); $env_key =~ tr{_}{.}; # Transliterate _ to +. # And put it into our array. push(@translated_env,"$env_key=$env_value"); } else { # Otherwise leave the environment variable unharmed. push(@translated_env,$_); } } [download] The code can certainly be reduced to a smaller number of steps, but I believe that maintainability is more important than clever tricks. It should be noted that the `m{...}x` construct allows whitespace (and comments) to be inserted without the meaning of the regexp changing. Also note that the assignment into `$env_key` and `$env_value` could be done inside the `if` condition, but results in a condition that I at least would consider too long. All the best, Paul Fenwick* Perl Training Australia	[reply] [d/l]
Re: substitution in a string by GrandFather (Saint) on Sep 28, 2005 at 08:41 UTC
If I understand your problem correctly the line of code you want is ~~`@newArray = (map {tr/_/./; $_} @array)`~~: `my @newArray = ( map {my ($lhs, $rhs) = /(.?)=(.)/; $lhs =~ tr/_/./; "$lhs=$rhs"} @array );` [download] Read more... test code (530 Bytes) Update: altered to only alter text to the left of `=` per pjf's suggestion Perl is Huffman encoded by design.	[reply] [d/l] [select]
Re^2: substitution in a string by pjf (Curate) on Sep 28, 2005 at 09:03 UTC
This solution works a treat provided that there are no underscores as part of the environment value. Unfortunately, for many systems these are common as parts of pathnames. A variable such as `oracle_home=/local_oracle/` would turn into `oracle.home=/local.oracle/`, which may not be desirable. If you were to split the keys from the values beforehand, then a map is an excellent way to perform the alterations. Cheerio, Paul Fenwick Perl Training Australia	[reply]
Re: substitution in a string by skillet-thief (Friar) on Sep 28, 2005 at 08:47 UTC
Two problems with the substitution you tried: `$temp = s\|_\|.\|;` [download] First, you need a tilde: `$temp =~ s///` Second, you need the `/g` operator so that more than just the first "_" is replaced. `$temp =~ s\|_\|.\|g;` `sub sk{ return unless $in = shift; $in =~ s!(.)$!!; print $1; sk($in)} sk("gro.alubaf@yehaf");` [download]	[reply] [d/l] [select]
Re: substitution in a string by Roy Johnson (Monsignor) on Sep 28, 2005 at 12:55 UTC
Here's an in-place edit: `s/([^=]+)/(my $lhs=$1) =~ tr:_:.:; $lhs/e for @envArray;` [download] Making it work on a copy is just a matter of `s/([^=]+)/(my $lhs=$1) =~ tr:_:.:; $lhs/e for @array=@envArray;` [download] Caution: Contents may have been coded under pressure.	[reply] [d/l] [select]
Re^2: substitution in a string by Roger_B (Scribe) on Sep 28, 2005 at 13:32 UTC
One problem with this - it will substitute . for _ in all environmental variables. How about `/^(?i:ORACLE_SID\|ORACLE_HST_SID\|ORACLE_HOME\|SDP_HOME)=/ && s/([^=]+)/(my $lhs=$1) =~ tr:_:.:; $lhs/e for @envArray;` Roger update: better idea by Roy Johnson below. Doh! However his code doesn't actually work because the brackets are the `(?imsx-imsx:pattern)` extension. Below is a possible fix: `s/^((?i)ORACLE_SID\|ORACLE_HST_SID\|ORACLE_HOME\|SDP_HOME)(?==)/(my $lhs=$1) =~ tr:_:.:; $lhs/e for @envArray;`	[reply] [d/l] [select]
Re^3: substitution in a string by Roy Johnson (Monsignor) on Sep 28, 2005 at 14:36 UTC
There's really no need to do a separate match and substitution, just change the pattern that the substitution matches: `s/^((?i:ORACLE_SID\|ORACLE_HST_SID\|ORACLE_HOME\|SDP_HOME))(?==)/(my $lhs +=$1) =~ tr:_:.:; $lhs/e for @envArray;` [download] (update: corrected the missing parens, as per Roger_B's update) Caution: Contents may have been coded under pressure.	[reply] [d/l]