In my bash script I have an external (received from user) string, which I should use in sed pattern.
REPLACE="<funny characters here>"
sed "s/KEYWORD/$REPLACE/g"
How can I escape the $REPLACE string so it would be safely accepted by sed as a literal replacement?
NOTE: The KEYWORD is a dumb substring with no matches etc. It is not supplied by user.
Warning: This does not consider newlines. For a more in-depth answer, see this SO-question instead. (Thanks, Ed Morton & Niklas Peter)
Note that escaping everything is a bad idea. Sed needs many characters to be escaped to get their special meaning. For example, if you escape a digit in the replacement string, it will turn in to a backreference.
As Ben Blank said, there are only three characters that need to be escaped in the replacement string (escapes themselves, forward slash for end of statement and & for replace all):
ESCAPED_REPLACE=$(printf '%s\n' "$REPLACE" | sed -e 's/[\/&]/\\&/g')
# Now you can use ESCAPED_REPLACE in the original sed statement
sed "s/KEYWORD/$ESCAPED_REPLACE/g"
If you ever need to escape the KEYWORD string, the following is the one you need:
sed -e 's/[]\/$*.^[]/\\&/g'
And can be used by:
KEYWORD="The Keyword You Need";
ESCAPED_KEYWORD=$(printf '%s\n' "$KEYWORD" | sed -e 's/[]\/$*.^[]/\\&/g');
# Now you can use it inside the original sed statement to replace text
sed "s/$ESCAPED_KEYWORD/$ESCAPED_REPLACE/g"
Remember, if you use a character other than / as delimiter, you need replace the slash in the expressions above wih the character you are using. See PeterJCLaw's comment for explanation.
Edited: Due to some corner cases previously not accounted for, the commands above have changed several times. Check the edit history for details.
The sed command allows you to use other characters instead of / as separator:
sed 's#"http://www\.fubar\.com"#URL_FUBAR#g'
The double quotes are not a problem.
The only three literal characters which are treated specially in the replace clause are / (to close the clause), \ (to escape characters, backreference, &c.), and & (to include the match in the replacement). Therefore, all you need to do is escape those three characters:
sed "s/KEYWORD/$(echo $REPLACE | sed -e 's/\\/\\\\/g; s/\//\\\//g; s/&/\\\&/g')/g"
Example:
$ export REPLACE="'\"|\\/><&!"
$ echo fooKEYWORDbar | sed "s/KEYWORD/$(echo $REPLACE | sed -e 's/\\/\\\\/g; s/\//\\\//g; s/&/\\\&/g')/g"
foo'"|\/><&!bar
Based on Pianosaurus's regular expressions, I made a bash function that escapes both keyword and replacement.
function sedeasy {
sed -i "s/$(echo $1 | sed -e 's/\([[\/.*]\|\]\)/\\&/g')/$(echo $2 | sed -e 's/[\/&]/\\&/g')/g" $3
}
Here's how you use it:
sedeasy "include /etc/nginx/conf.d/*" "include /apps/*/conf/nginx.conf" /etc/nginx/nginx.conf
It's a bit late to respond... but there IS a much simpler way to do this. Just change the delimiter (i.e., the character that separates fields). So, instead of s/foo/bar/ you write s|bar|foo.
And, here's the easy way to do this:
sed 's|/\*!50017 DEFINER=`snafu`#`localhost`\*/||g'
The resulting output is devoid of that nasty DEFINER clause.
It turns out you're asking the wrong question. I also asked the wrong question. The reason it's wrong is the beginning of the first sentence: "In my bash script...".
I had the same question & made the same mistake. If you're using bash, you don't need to use sed to do string replacements (and it's much cleaner to use the replace feature built into bash).
Instead of something like, for example:
function escape-all-funny-characters() { UNKNOWN_CODE_THAT_ANSWERS_THE_QUESTION_YOU_ASKED; }
INPUT='some long string with KEYWORD that need replacing KEYWORD.'
A="$(escape-all-funny-characters 'KEYWORD')"
B="$(escape-all-funny-characters '<funny characters here>')"
OUTPUT="$(sed "s/$A/$B/g" <<<"$INPUT")"
you can use bash features exclusively:
INPUT='some long string with KEYWORD that need replacing KEYWORD.'
A='KEYWORD'
B='<funny characters here>'
OUTPUT="${INPUT//"$A"/"$B"}"
Use awk - it is cleaner:
$ awk -v R='//addr:\\file' '{ sub("THIS", R, $0); print $0 }' <<< "http://file:\_THIS_/path/to/a/file\\is\\\a\\ nightmare"
http://file:\_//addr:\file_/path/to/a/file\\is\\\a\\ nightmare
Here is an example of an AWK I used a while ago. It is an AWK that prints new AWKS. AWK and SED being similar it may be a good template.
ls | awk '{ print "awk " "'"'"'" " {print $1,$2,$3} " "'"'"'" " " $1 ".old_ext > " $1 ".new_ext" }' > for_the_birds
It looks excessive, but somehow that combination of quotes works to keep the ' printed as literals. Then if I remember correctly the vaiables are just surrounded with quotes like this: "$1". Try it, let me know how it works with SED.
These are the escape codes that I've found:
* = \x2a
( = \x28
) = \x29
" = \x22
/ = \x2f
\ = \x5c
' = \x27
? = \x3f
% = \x25
^ = \x5e
sed is typically a mess, especially the difference between gnu-sed and bsd-sed
might just be easier to place some sort of sentinel at the sed side, then a quick pipe over to awk, which is far more flexible in accepting any ERE regex, escaped hex, or escaped octals.
e.g. OFS in awk is the true replacement ::
date | sed -E 's/[0-9]+/\xC1\xC0/g' |
mawk NF=NF FS='\xC1\xC0' OFS='\360\237\244\241'
1 Tue Aug 🤡 🤡:🤡:🤡 EDT 🤡
(tested and confirmed working on both BSD-sed and GNU-sed - the emoji isn't a typo that's what those 4 bytes map to in UTF-8 )
There are dozens of answers out there... If you don't mind using a bash function schema, below is a good answer. The objective below was to allow using sed with practically any parameter as a KEYWORD (F_PS_TARGET) or as a REPLACE (F_PS_REPLACE). We tested it in many scenarios and it seems to be pretty safe. The implementation below supports tabs, line breaks and sigle quotes for both KEYWORD and replace REPLACE.
NOTES: The idea here is to use sed to escape entries for another sed command.
CODE
F_REVERSE_STRING_R=""
f_reverse_string() {
: 'Do a string reverse.
To undo just use a reversed string as STRING_INPUT.
Args:
STRING_INPUT (str): String input.
Returns:
F_REVERSE_STRING_R (str): The modified string.
'
local STRING_INPUT=$1
F_REVERSE_STRING_R=$(echo "x${STRING_INPUT}x" | tac | rev)
F_REVERSE_STRING_R=${F_REVERSE_STRING_R%?}
F_REVERSE_STRING_R=${F_REVERSE_STRING_R#?}
}
# [Ref(s).: https://stackoverflow.com/a/2705678/3223785 ]
F_POWER_SED_ECP_R=""
f_power_sed_ecp() {
: 'Escape strings for the "sed" command.
Escaped characters will be processed as is (e.g. /n, /t ...).
Args:
F_PSE_VAL_TO_ECP (str): Value to be escaped.
F_PSE_ECP_TYPE (int): 0 - For the TARGET value; 1 - For the REPLACE value.
Returns:
F_POWER_SED_ECP_R (str): Escaped value.
'
local F_PSE_VAL_TO_ECP=$1
local F_PSE_ECP_TYPE=$2
# NOTE: Operational characters of "sed" will be escaped, as well as single quotes.
# By Questor
if [ ${F_PSE_ECP_TYPE} -eq 0 ] ; then
# NOTE: For the TARGET value. By Questor
F_POWER_SED_ECP_R=$(echo "x${F_PSE_VAL_TO_ECP}x" | sed 's/[]\/$*.^[]/\\&/g' | sed "s/'/\\\x27/g" | sed ':a;N;$!ba;s/\n/\\n/g')
else
# NOTE: For the REPLACE value. By Questor
F_POWER_SED_ECP_R=$(echo "x${F_PSE_VAL_TO_ECP}x" | sed 's/[\/&]/\\&/g' | sed "s/'/\\\x27/g" | sed ':a;N;$!ba;s/\n/\\n/g')
fi
F_POWER_SED_ECP_R=${F_POWER_SED_ECP_R%?}
F_POWER_SED_ECP_R=${F_POWER_SED_ECP_R#?}
}
# [Ref(s).: https://stackoverflow.com/a/24134488/3223785 ,
# https://stackoverflow.com/a/21740695/3223785 ,
# https://unix.stackexchange.com/a/655558/61742 ,
# https://stackoverflow.com/a/11461628/3223785 ,
# https://stackoverflow.com/a/45151986/3223785 ,
# https://linuxaria.com/pills/tac-and-rev-to-see-files-in-reverse-order ,
# https://unix.stackexchange.com/a/631355/61742 ]
F_POWER_SED_R=""
f_power_sed() {
: 'Facilitate the use of the "sed" command. Replaces in files and strings.
Args:
F_PS_TARGET (str): Value to be replaced by the value of F_PS_REPLACE.
F_PS_REPLACE (str): Value that will replace F_PS_TARGET.
F_PS_FILE (Optional[str]): File in which the replacement will be made.
F_PS_SOURCE (Optional[str]): String to be manipulated in case "F_PS_FILE" was
not informed.
F_PS_NTH_OCCUR (Optional[int]): [1~n] - Replace the nth match; [n~-1] - Replace
the last nth match; 0 - Replace every match; Default 1.
Returns:
F_POWER_SED_R (str): Return the result if "F_PS_FILE" is not informed.
'
local F_PS_TARGET=$1
local F_PS_REPLACE=$2
local F_PS_FILE=$3
local F_PS_SOURCE=$4
local F_PS_NTH_OCCUR=$5
if [ -z "$F_PS_NTH_OCCUR" ] ; then
F_PS_NTH_OCCUR=1
fi
local F_PS_REVERSE_MODE=0
if [ ${F_PS_NTH_OCCUR} -lt -1 ] ; then
F_PS_REVERSE_MODE=1
f_reverse_string "$F_PS_TARGET"
F_PS_TARGET="$F_REVERSE_STRING_R"
f_reverse_string "$F_PS_REPLACE"
F_PS_REPLACE="$F_REVERSE_STRING_R"
f_reverse_string "$F_PS_SOURCE"
F_PS_SOURCE="$F_REVERSE_STRING_R"
F_PS_NTH_OCCUR=$((-F_PS_NTH_OCCUR))
fi
f_power_sed_ecp "$F_PS_TARGET" 0
F_PS_TARGET=$F_POWER_SED_ECP_R
f_power_sed_ecp "$F_PS_REPLACE" 1
F_PS_REPLACE=$F_POWER_SED_ECP_R
local F_PS_SED_RPL=""
if [ ${F_PS_NTH_OCCUR} -eq -1 ] ; then
# NOTE: We kept this option because it performs better when we only need to replace
# the last occurrence. By Questor
# [Ref(s).: https://linuxhint.com/use-sed-replace-last-occurrence/ ,
# https://unix.stackexchange.com/a/713866/61742 ]
F_PS_SED_RPL="'s/\(.*\)$F_PS_TARGET/\1$F_PS_REPLACE/'"
elif [ ${F_PS_NTH_OCCUR} -gt 0 ] ; then
# [Ref(s).: https://unix.stackexchange.com/a/587924/61742 ]
F_PS_SED_RPL="'s/$F_PS_TARGET/$F_PS_REPLACE/$F_PS_NTH_OCCUR'"
elif [ ${F_PS_NTH_OCCUR} -eq 0 ] ; then
F_PS_SED_RPL="'s/$F_PS_TARGET/$F_PS_REPLACE/g'"
fi
# NOTE: As the "sed" commands below always process literal values for the "F_PS_TARGET"
# so we use the "-z" flag in case it has multiple lines. By Quaestor
# [Ref(s).: https://unix.stackexchange.com/a/525524/61742 ]
if [ -z "$F_PS_FILE" ] ; then
F_POWER_SED_R=$(echo "x${F_PS_SOURCE}x" | eval "sed -z $F_PS_SED_RPL")
F_POWER_SED_R=${F_POWER_SED_R%?}
F_POWER_SED_R=${F_POWER_SED_R#?}
if [ ${F_PS_REVERSE_MODE} -eq 1 ] ; then
f_reverse_string "$F_POWER_SED_R"
F_POWER_SED_R="$F_REVERSE_STRING_R"
fi
else
if [ ${F_PS_REVERSE_MODE} -eq 0 ] ; then
eval "sed -i -z $F_PS_SED_RPL \"$F_PS_FILE\""
else
tac "$F_PS_FILE" | rev | eval "sed -z $F_PS_SED_RPL" | tac | rev > "$F_PS_FILE"
fi
fi
}
MODEL
f_power_sed "F_PS_TARGET" "F_PS_REPLACE" "" "F_PS_SOURCE"
echo "$F_POWER_SED_R"
EXAMPLE
f_power_sed "{ gsub(/,[ ]+|$/,\"\0\"); print }' ./ and eliminate" "[ ]+|$/,\"\0\"" "" "Great answer (+1). If you change your awk to awk '{ gsub(/,[ ]+|$/,\"\0\"); print }' ./ and eliminate that concatenation of the final \", \" then you don't have to go through the gymnastics on eliminating the final record. So: readarray -td '' a < <(awk '{ gsub(/,[ ]+/,\"\0\"); print; }' <<<\"$string\") on Bash that supports readarray. Note your method is Bash 4.4+ I think because of the -d in readar"
echo "$F_POWER_SED_R"
IF YOU JUST WANT TO ESCAPE THE PARAMETERS TO THE SED COMMAND
MODEL
# "TARGET" value.
f_power_sed_ecp "F_PSE_VAL_TO_ECP" 0
echo "$F_POWER_SED_ECP_R"
# "REPLACE" value.
f_power_sed_ecp "F_PSE_VAL_TO_ECP" 1
echo "$F_POWER_SED_ECP_R"
IMPORTANT: If the strings for KEYWORD and/or replace REPLACE contain tabs or line breaks you will need to use the "-z" flag in your "sed" command. More details here.
EXAMPLE
f_power_sed_ecp "{ gsub(/,[ ]+|$/,\"\0\"); print }' ./ and eliminate" 0
echo "$F_POWER_SED_ECP_R"
f_power_sed_ecp "[ ]+|$/,\"\0\"" 1
echo "$F_POWER_SED_ECP_R"
NOTE: The f_power_sed_ecp and f_power_sed functions above was made available completely free as part of this project ez_i - Create shell script installers easily!.
Standard recommendation here: use perl :)
echo KEYWORD > /tmp/test
REPLACE="<funny characters here>"
perl -pi.bck -e "s/KEYWORD/${REPLACE}/g" /tmp/test
cat /tmp/test
don't forget all the pleasure that occur with the shell limitation around " and '
so (in ksh)
Var=">New version of \"content' here <"
printf "%s" "${Var}" | sed "s/[&\/\\\\*\\"']/\\&/g' | read -r EscVar
echo "Here is your \"text\" to change" | sed "s/text/${EscVar}/g"
If the case happens to be that you are generating a random password to pass to sed replace pattern, then you choose to be careful about which set of characters in the random string. If you choose a password made by encoding a value as base64, then there is is only character that is both possible in base64 and is also a special character in sed replace pattern. That character is "/", and is easily removed from the password you are generating:
# password 32 characters log, minus any copies of the "/" character.
pass=`openssl rand -base64 32 | sed -e 's/\///g'`;
If you are just looking to replace Variable value in sed command then just remove
Example:
sed -i 's/dev-/dev-$ENV/g' test to sed -i s/dev-/dev-$ENV/g test
I have an improvement over the sedeasy function, which WILL break with special characters like tab.
function sedeasy_improved {
sed -i "s/$(
echo "$1" | sed -e 's/\([[\/.*]\|\]\)/\\&/g'
| sed -e 's:\t:\\t:g'
)/$(
echo "$2" | sed -e 's/[\/&]/\\&/g'
| sed -e 's:\t:\\t:g'
)/g" "$3"
}
So, whats different? $1 and $2 wrapped in quotes to avoid shell expansions and preserve tabs or double spaces.
Additional piping | sed -e 's:\t:\\t:g' (I like : as token) which transforms a tab in \t.
An easier way to do this is simply building the string before hand and using it as a parameter for sed
rpstring="s/KEYWORD/$REPLACE/g"
sed -i $rpstring test.txt
I have a perl inline replace command in a shell script that isn't working for some reason. With below command, its replacing all ":" with replacement string in the perl command.
When I manually ssh to the box and running the perl command works as expected.
ssh host "cd /x/somedirectory && perl -pi -e 's#\${somehost}:\${someport}#10.20.30.40:8443#g' config/app.properties"
Edit1
Please note that $somehost and $someport are NOT shell variables. I'm looking for a literal text replacement.
What am I doing wrong? I tried using different delimiters, escaping { and } etc but still no luck.
To create a single-quoted shell literal from a string, escape ' by replacing them with '\''.
To create a double-quoted shell literal from a string, escape \, " and $ by prefixing them with \.
The Perl command you want is
s#\${somehost}:\${someport}#10.20.30.40:8443#g
So the remote shell command you want is
perl -pi -e 's#\${somehost}:\${someport}#10.20.30.40:8443#g' config/app.properties
So the local shell command you want is
ssh host 'perl -pi -e '\''s#\${somehost}:\${someport}#10.20.30.40:8443#g'\'' config/app.properties'
or
ssh host "perl -pi -e 's#\\\${somehost}:\\\${someport}#10.20.30.40:8443#g' config/app.properties"
[Removed cd /x/somedirectory && to keep things simple. Just add it back in.]
The shell on the remote machine will perform another level of escaping. To receive the sequence \$ on the remote machine you have to send the sequence \\\$:
ssh host "cd /x/somedirectory && perl -pi -e
's#\\\${somehost}:\\\${someport}#10.20.30.40:8443#g' config/app.properties"
So, you can write Perl...
#!/usr/bin/perl
use Net::OpenSSH;
my $ssh = Net::OpenSSH->new($host);
my $old = quotemeta("${somehost}:${someport}");
$ssh->system('cd', $some_directory, \\'&&',
'perl', '-pi', '-e',
"s|$old|10.20.30.40:8443|g",
'config/app.properties');
Try this ssh command with here-doc and avoid all escaping:
ssh -t -t host<<'EOF'
cd /x/somedirectory &&
perl -i -pe 's#\${somehost}:\${someport}#10.20.30.40:8443#g' config/app.properties
exit
EOF
For a list of files, I'd like to match the ones not ending with .txt. I am currently using this expression:
.*(txt$)|(html\.txt$)
This expression will match everything ending in .txt, but I'd like it to do the opposite.
Should match:
happiness.html
joy.png
fear.src
Should not match:
madness.html.txt
excitement.txt
I'd like to get this so I can use it in pair with fswatch:
fswatch -0 -e 'regex here' . | xargs -0 -n 1 -I {} echo "{} has been changed"
The problem is it doesn't seem to work.
PS: I use the tag bash instead of fswatch because I don't have enough reputation points to create it. Sorry!
Try using a lookbehind, like this:
.*$(?<!\.txt)
Demonstration
Basically, this matches any line of text so long as the last 4 characters are not ".txt".
You can use Negative Lookahead for this purpose.
^(?!.*\.txt).+$
Live Demo
You can use this expression with grep using option -P:
grep -Po '^(?!.*\.txt).+$' file
Since question has been tagged as bash, lookaheads may not be supported (except grep -P), here is one grep solution that doesn't need lookaheads:
grep -v '\.txt$' file
happiness.html
joy.png
fear.src
EDIT: You can use this xargs command to avoid matching *.txt files:
xargs -0 -n 1 -I {} bash -c '[[ "{}" == *".txt" ]] && echo "{} has been changed"'
It really depends what regular expression tool you are using. Many tools provide a way to invert the sense of a regex. For example:
bash
# succeeds if filename ends with .txt
[[ $filename =~ "."txt$ ]]
# succeeds if filename does not end with .txt
! [[ $filename =~ "."txt$ ]]
# another way of writing the negative
[[ ! $filename =~ "."txt$ ]]
grep
# succeeds if filename ends with .txt
egrep -q "\.txt$" <<<"$filename"
# succeeds if filename does not end with .txt
egrep -qv "\.txt$" <<<"$filename"
awk
/\.txt$/ { print "line ends with .txt" }
! /\.txt$/ { print "line doesn't end with .txt" }
$1 ~ /\.txt$/ { print "first field ends with .txt" }
$1 !~ /\.txt$/ { print "first field doesn't end with .txt" }
For the adventurous, a posix ERE which will work in any posix compatible regex engine
/[^t]$|[^x]t$|[^t]xt$|[^.]txt$/
I have a bash script that I copy and run on both linux and AIX servers.
This script gets a "name" parameter which represents a file name, and I need to manipulate this name via regex (the purpose is irrelevant and very hard to explain).
From the name parameter I need to take the beginning until the first "-" character that is followed by a digit, and then concat it with the last "." character until the end of the string.
For example:
name: abcd-efg-1.23.4567-8.jar will become: abcd-efg.jar
name: abc123-abc3.jar will remain: abc123-abc3.jar
name: abc-890.jar will become: abc.jar
I've tried several variations of:
name=$1
regExpr="^(.*?)-\d.*\.(.*?)$/g"
echo $name
echo $(printf ${name} | sed -e $regExpr)
Also I cant use sed -r (seen on some examples) because AIX sed does not support the -r flag.
The last line is the problem of course; I think I need to somehow use $1 + $2 placeholders, but I can't seem to get it right.
How can I change my regex so that it does what I want?
Given the file:
abcd-efg-1.23.4567-8.jar
abc123-abc3.jar
abc-890.jar
This is a way to change the names you give:
$ sed 's/\(.\?\)-[0-9].*\(\.[a-z]*\)$/\1\2/' file
abcd-efg.jar
abc123-abc3.jar
abc.jar
Which is equivalent to (if you could use -r):
$ sed -r 's/(.?)-[0-9].*(\.[a-z]*)$/\1\2/' file
abcd-efg.jar
abc123-abc3.jar
abc.jar
It gets everything up to - + digit and "stores" in \1.
It gets from last . + letters and "stores" in \2.
Finally it prints those blocks back.
Note the extension could also be fetched with the basename builtin or with something like `"${line##*.}".
You could use this:
perl -F'(-(?:\d)|\.)' -ane 'print "$F[0].$F[$#F]"'
It splits the input on any - followed by a digit, or any .. Then it prints the first field, followed by a dot, followed by the last field.
Testing it out:
$ cat file
abcd-efg-1.23.4567-8.jar
abc123-abc3.jar
abc-890.jar
$ perl -F'(-(?:\d)|\.)' -ane 'print "$F[0].$F[$#F]"' file
abcd-efg.jar
abc123-abc3.jar
abc.jar
In sed, you could simply use the following.
#!/bin/sh
STRING=$( cat <<EOF
abcd-efg-1.23.4567-8.jar
abc123-abc3.jar
abc-890.jar
EOF
)
echo "$STRING" | sed 's/-[0-9].*\(\.[^.]\+\)$/\1/'
# abcd-efg.jar
# abc123-abc3.jar
# abc.jar
This matches a hyphen followed by a number and everything after and replaces with the file extension.
Or you may consider using a Perl one-liner:
echo "$STRING" | perl -pe 's/-\d.*(?=\.[^.]+$)//'
# abcd-efg.jar
# abc123-abc3.jar
# abc.jar
when a successful regex match is made, perl will capture whatever is matched in parenthesis ( .. ) as $1, $2, etc.
$ perl -e 'my $arg = $ARGV[0]; $arg =~ /^(.*?)-\d.*\.(.*?)$/; print "$1.$2\n"; ' abc-890.jar
abc.jar
I expected this to capture and print just the group defined in parens, but instead it prints the whole line. How can I capture and print just the group in parens?
echo "abcdef" | perl -ne "print $1 if /(cd)/ "
What I want this to print: cd
What it actually prints: abcdef
How to fix?
In the perl command, you have to use single quotes or protect variables :
echo "abcdef" | perl -ne "print \$1 if /(cd)/"
or
echo "abcdef" | perl -ne 'print $1 if /(cd)/'
In double quotes, the shell expand $1.
The instant fix to your question is to change your double quotes to single quotes, like this:
$ echo abcdef | perl -ne 'print $1 if /(cd)/'
cd
With double quotes, the shell environment interprets your unprotected variable $1, which in your environment apparently evaluates to an empty string. So perl only receives the command print if /(cd)/ which is an implied command print $_ if /(cd)/ which prints the entire line.
You can also use a protected variable like this:
$ echo abcdef | perl -ne "print \$1 if /(cd)/"
cd
Note that matches which use different delimiters (other than / and /) are required to begin with the m keyword rather than using the shorthand form. But in your case, this does not matter, but it is often something worth being aware of when working with matches, e.g., m|/| would match a / character using the pipe as the delimiter for the regular expression.