backslashes in perl substitution - perl

I'm trying my luck with a perl one-liner changing some commands in a bunch of .tex files. I got as far as the following:
perl -pi -e "s/\Q\linenum{some more stuff}\E/\Q\uln\E/g" *tex
Which results in \lLn instead of the expected replacement patter \uln. Apparently while \Q and \E take care of other special characters, they don't take care of the \l \u changing the case of the next character, how would I do that?

\Q\E works best for \Q$var\E. Elsewhere, you can use \ to escape characters that need escaping.
perl -i -pe's/\\linenum\{some more stuff\}/\\uln/g' *tex

Related

sed command over multiple lines not working

I am using sed to replace 14 different abbreviations like CA_23456, CB_scaffold34532,... with 'proper' names in a file and it works putting it all on one line.
acc=$1
sed -e 's/CA_[A-Z]*[a-z]*[0-9]*/Hesperocyparis_arizonica/;s/CB_[A-Z]*[a-z]*[0-9]*/Hesperocyparis_bakeri/;s/CM_[A-Z]*[a-z]*[0-9]*/Hesperocyparis_macrocarpa/;s/CS_[A-Z]*[a-z]*[0-9]*/Cupressus_sempervirens/;s/CT_[A-Z]*[a-z]*[0-9]*/Cupressus_torulosa/;s/JD_[A-Z]*[a-z]*[0-9]*/Juniperus_drupacea/;s/JF_[A-Z]*[a-z]*[0-9]*/Juniperus_flaccida/;s/JI_[A-Z]*[a-z]*[0-9]*/Juniperus_indica/;s/JP_[A-Z]*[a-z]*[0-9]*/Juniperus_phoenicea/;s/JX_[A-Z]*[a-z]*[0-9]*/Juniperus_procera/;s/JS_[A-Z]*[a-z]*[0-9]*/Juniperus_scopulorum/;s/MD_[A-Z]*[a-z]*[0-9]*/Microbiota_decussata/;s/XN_[A-Z]*[a-z]*[0-9]*/Xanthocyparis_nootkatensis/;s/XV_[A-Z]*[a-z]*[0-9]*/Xanthocyparis_vietnamensis/' ${acc}.nex > ${acc}_replaced.nex
To make it more readable I'd like to have the command split over multiple lines using '\' (not all the replacements are shown for brevity)
acc=$1
sed -e 's/CA_[A-Z]*[a-z]*[0-9]*/Hesperocyparis_arizonica/;\
s/CB_[A-Z]*[a-z]*[0-9]*/Hesperocyparis_bakeri/;\
s/CM_[A-Z]*[a-z]*[0-9]*/Hesperocyparis_macrocarpa/'\
${acc}.nex > ${acc}_replaced.nex
However, I get an error message: sed: -e expression #1, char 168: unterminated address regex. I have looked at the answers to similar problems on various webforums and tried various things (using 's/.../.../' on every line, leaving ';' out,....) but I can't get it to work. What am I doing wrong?
Drop the \ that escapes the newlines. (They are not actually doing it!, they are interpreted as wrong syntax by sed). However I would suggest to put it into a file and run it like this:
sed -f script.sed input
where script.sed looks like this:
s/CA_[A-Z]*[a-z]*[0-9]*/Hesperocyparis_arizonica/
s/CB_[A-Z]*[a-z]*[0-9]*/Hesperocyparis_bakeri/
s/CM_[A-Z]*[a-z]*[0-9]*/Hesperocyparis_macrocarpa/
Remove the backslashes from the sed code.
Inside singly-quoted shell strings, backslashes are not needed to escape newlines and are not removed because they are not parsed as escape characters. This has the effect that sed sees them as part of its code, and it then expects to find an address regex with a different delimiter than / before the command ends at the next newline (similar to \,/home/, !d). This address regex does not appear (nor an associated command), and so sed complains about invalid code.
Apart from that: The semicolons in the sed code are no longer necessary when you terminate commands with newlines, and anything involving shell variables should be quoted to avoid splitting in case of whitespace.
In sum:
sed -e 's/CA_[A-Z]*[a-z]*[0-9]*/Hesperocyparis_arizonica/
s/CB_[A-Z]*[a-z]*[0-9]*/Hesperocyparis_bakeri/
s/CM_[A-Z]*[a-z]*[0-9]*/Hesperocyparis_macrocarpa/' \
"${acc}.nex" > "${acc}_replaced.nex"

sed and perl not replacing a letter in a file

I have a file 1.htm. I want to replace a letter ṣ (s with dot below). I tried with both sed and perl and it does not replace.
sed -i 's/ṣ/s/g' "1.htm"
perl -i -pe 's/ṣ/s/g' "1.htm"
can anyone suggest what to do
1.html (not replacing ṣ)
Also i have found another strange thing. Sed (same command as above) replaces in one file but not the other I am putting the links
replacable.html
unreplacable.html same as 1.html
Why is it happening so. sed is able to replace ṣ in one file but not the other.
You have combined characters in the html file. That is, the "ṣ" is really a "s" followed by a " ̣" (a COMBINING DOT BELOW). One possibility to fix the oneliner is:
perl -C -i -pe 's/s\x{0323}/s/g' "1.htm"
That is, turn utf8 mode for stdout/stdin on (-C) and explicitely write the two characters in the left side of the s///.
Another possibility is to normalize all the combining characters using Unicode::Normalize, e.g.:
perl -C -MUnicode::Normalize -Mutf8 -i -pe '$_=NFKC($_); s/ṣ/s/g' "1.htm"
But this would also normalize all the other characters in the input file, which may or may not be OK for you.
This might work for you (GNU sed):
sed 's/\o341\o271\o243/s/g' file
To find seds octal interpretation of a character use:
echo 'ṣ'| sed l
This returns (for me):
\341\271\243$
ṣ
Then use \onnn (or combinations of) to find the correct pattern in the lefthandside (LFH) of the substitute command.
N.B. \onnn may also be used in the RHS of the substitute command.

Replacing a part of a line with bash / perl

I'm a noob at bash need to replace the mypassword part of this line in a file
"rpc-password": mypassword
with mynewpassword
I tried
perl -pi -e "s,PASSWORD,${password},g" "${user_conf}"
but it dosen't seem to do anything :(
I can use anything that will work inside a bash script, it dosen't have to be bash or perl.
perl -pi -e 's/mypassword/mynewpassword/g' file
will work
Using a loose regex without keeping backups is a bad idea. Especially if you intend to use dynamic replacement strings. While it may work just fine for something like "mypassword", it will break if someone tries to replace with the password "ass" with "butt":
"rpc-password": mypassword
Would become:
"rpc-pbuttword": butt
The more automation you seek, the more strict you need the regex to be, IMO.
I would anchor the replacement part to the particular configuration line that you seek:
s/^\s*"rpc-password":\s*\K\Q$mypassword\E\s*$/$mynewpassword/
No /g modifier, unless you intend to replace a password several times on the same line. \K will preserve the characters before it. Using \s* liberally will be a safeguard against user-edited configuration files where extra whitespace might have been added.
Also, importantly, you need to quote meta characters in the password. Otherwise a password such as t(foo)? Will also match a single t. In general, it will cause strange mismatches. This is why I added \Q...\E (see perldoc perlre) to the regex, which will allow variable interpolation, but escape meta characters.
You can also use sed for this:
sed -i 's/mypassword/mynewpassword/g' file

sed rare-delimiter (other than & | / ?...)

I am using the Unix sed command on a string that can contain all types of characters (&, |, !, /, ?, etc).
Is there a complex delimiter (with two characters?) that can fix the error:
sed: -e expression #1, char 22: unknown option to `s'
The characters in the input file are of no concern - sed parses them fine. There may be an issue, however, if you have most of the common characters in your pattern - or if your pattern may not be known beforehand.
At least on GNU sed, you can use a non-printable character that is highly improbable to exist in your pattern as a delimiter. For example, if your shell is Bash:
$ echo '|||' | sed s$'\001''|'$'\001''/'$'\001''g'
In this example, Bash replaces $'\001' with the character that has the octal value 001 - in ASCII it's the SOH character (start of heading).
Since such characters are control/non-printable characters, it's doubtful that they will exist in the pattern. Unless, that is, you are doing something weird like modifying binary files - or Unicode files without the proper locale settings.
Another way to do this is to use Shell Parameter Substitution.
${parameter/pattern/replace} # substitute replace for pattern once
or
${parameter//pattern/replace} # substitute replace for pattern everywhere
Here is a quite complex example that is difficult with sed:
$ parameter="Common sed delimiters: [sed-del]"
$ pattern="\[sed-del\]"
$ replace="[/_%:\\#]"
$ echo "${parameter//$pattern/replace}"
result is:
Common sed delimiters: [/_%:\#]
However: This only work with bash parameters and not files where sed excel.
There is no such option for multi-character expression delimiters in sed, but I doubt
you need that. The delimiter character should not occur in the pattern, but if it appears in the string being processed, it's not a problem. And unless you're doing something extremely weird, there will always be some character that doesn't appear in your search pattern that can serve as a delimiter.
You need the nested delimiter facility that Perl offers. That allows to use stuff like matching, substituting, and transliterating without worrying about the delimiter being included in your contents. Since perl is a superset of sed, you should be able to use it for whatever you’re used sed for.
Consider this:
$ perl -nle 'print if /something/' inputs
Now if your something contains a slash, you have a problem. The way to fix this is to change delimiter, preferably to a bracketing one. So for example, you could having anything you like in the $WHATEVER shell variable (provided the backets are balanced), which gets interpolated by the shell before Perl is even called here:
$ perl -nle "print if m($WHATEVER)" /usr/share/dict/words
That works even if you have correctly nested parens in $WHATEVER. The four bracketing pairs which correctly nest like this in Perl are < >, ( ), [ ], and { }. They allow arbitrary contents that include the delimiter if that delimiter is balanced.
If it is not balanced, then do not use a delimiter at all. If the pattern is in a Perl variable, you don’t need to use the match operator provided you use the =~ operator, so:
$whatever = "some arbitrary string ( / # [ etc";
if ($line =~ $whatever) { ... }
With the help of Jim Lewis, I finally did a test before using sed :
if [ `echo $1 | grep '|'` ]; then
grep ".*$1.*:" $DB_FILE | sed "s#^.*$1*.*\(:\)## "
else
grep ".*$1.*:" $DB_FILE | sed "s|^.*$1*.*\(:\)|| "
fi
Thanks for help
Wow. I totally did not know that you could use any character as a delimiter.
At least half the time I use the sed and BREs its on paths, code snippets, junk characters, things like that. I end up with a bunch of horribly unreadable escapes which I'm not even sure won't die on some combination I didn't think of. But if you can exclude just some character class (or just one character even)
echo '#01Y $#1+!' | sed -e 'sa$#1+ashita' -e 'su#01YuHolyug'
> > > Holy shit!
That's so much easier.
Escaping the delimiter inline for BASH to parse is cumbersome and difficult to read (although the delimiter does need escaping for sed's benefit when it's first used, per-expression).
To pull together thkala's answer and user4401178's comment:
DELIM=$(echo -en "\001");
sed -n "\\${DELIM}${STARTING_SEARCH_TERM}${DELIM},\\${DELIM}${ENDING_SEARCH_TERM}${DELIM}p" "${FILE}"
This example returns all results starting from ${STARTING_SEARCH_TERM} until ${ENDING_SEARCH_TERM} that don't match the SOH (start of heading) character with ASCII code 001.
There's no universal separator, but it can be escaped by a backslash for sed to not treat it like separator (at least unless you choose a backslash character as separator).
Depending on the actual application, it might be handy to just escape those characters in both pattern and replacement.
If you're in a bash environment, you can use bash substitution to escape sed separator, like this:
safe_replace () {
sed "s/${1//\//\\\/}/${2//\//\\\/}/g"
}
It's pretty self-explanatory, except for the bizarre part.
Explanation to that:
${1//\//\\\/}
${ - bash expansion starts
1 - first positional argument - the pattern
// - bash pattern substitution pattern separator "replace-all" variant
\/ - literal slash
/ - bash pattern substitution replacement separator
\\ - literal backslash
\/ - literal slash
} - bash expansion ends
example use:
$ input="ka/pus/ta"
$ pattern="/pus/"
$ replacement="/re/"
$ safe_replace "$pattern" "$replacement" <<< "$input"
ka/re/ta

How can I remove all non-word characters except the newline?

I have a file like this:
my line - some words & text
oh lóok i've got some characters
I want to 'normalize' it and remove all the non-word characters. I want to end up with something like this:
mylinesomewordstext
ohlóokivegotsomecharacters
I'm using Linux on the command line at the moment, and I'm hoping there's some one-liner I can use.
I tried this:
cat file | perl -pe 's/\W//'
But that removed all the newlines and put everything one line. Is there someway I can tell Perl to not include newlines in the \W? Or is there some other way?
This removes characters that don't match \w or \n:
cat file | perl -C -pe 's/[^\w\n]//g'
#sth's solution uses Perl, which is (at least on my system) not Unicode compatible, thus it loses the accented o character.
On the other hand, sed is Unicode compatible (according to the lists on this page), and gives a correct result:
$ sed 's/\W//g' a.txt
mylinesomewordstext
ohlóokivegotsomecharacters
In Perl, I'd just add the -l switch, which re-adds the newline by appending it to the end of every print():
perl -ple 's/\W//g' file
Notice that you don't need the cat.
The previous response isn't echoing the "ó" character. At least in my case.
sed 's/\W//g' file
Best practices for shell scripting dictate that you should use the tr program for replacing single characters instead of sed, because it's faster and more efficient. Obviously use sed if replacing longer strings.
tr -d '[:blank:][:punct:]' < file
When run with time I get:
real 0m0.003s
user 0m0.000s
sys 0m0.004s
When I run the sed answer (sed -e 's/\W//g' file) with time I get:
real 0m0.003s
user 0m0.004s
sys 0m0.004s
While not a "huge" difference, you'll notice the difference when running against larger data sets. Also please notice how I didn't pipe cat's output into tr, instead using I/O redirection (one less process to spawn).