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How can I use sed to add a dynamic prefix to each number in an integer list?
For example:
I have a string "A-1,2,3,4,5", I want to transform it to string "A-1,A-2,A-3,A-4,A-5" - which means I want to add prefix of first integer i.e. "A-" to each number of the list.
If I have string like "B-1,20,300" then I want to transform it to string "B-1,B-20,B-300".
I am not able to use RegEx Capturing Groups because for global match they do not retain their value in subsequent matches.
When it comes to looping constructs in sed, I like to use newlines as markers for the places I have yet to process. This makes matching much simpler, and I know they're not in the input because my input is a text line.
For example:
$ echo A-1,2,3,4,5 | sed 's/,/\n/g;:a s/^\([^0-9]*\)\([^\n]*\)\n/\1\2,\1/; ta'
A-1,A-2,A-3,A-4,A-5
This works as follows:
s/,/\n/g # replace all commas with newlines (insert markers)
:a # label for looping
s/^\([^0-9]*\)\([^\n]*\)\n/\1\2,\1/ # replace the next marker with a comma followed
# by the prefix
ta # loop unless there's nothing more to do.
The approach is similar to #potong's, but I find the regex much more readable -- \([^0-9]*\) captures the prefix, \([^\n]*\) captures everything up to the next marker (i.e. everything that's already been processed), and then it's just a matter of reassembling it in the substitution.
Don't use sed, just use the other standard UNIX text manipulation tool, awk:
$ echo 'A-1,2,3,4,5' | awk '{p=substr($0,1,2); gsub(/,/,"&"p)}1'
A-1,A-2,A-3,A-4,A-5
$ echo 'B-1,20,300' | awk '{p=substr($0,1,2); gsub(/,/,"&"p)}1'
B-1,B-20,B-300
This might work for you (GNU sed):
sed -E ':a;s/^((([^-]+-)[^,]+,)+)([0-9])/\1\3\4/;ta' file
Uses pattern matching and a loop to replace a number following a comma by the first column prefix and that number.
Assuming this is for shell scripting, you can do so with 2 seds:
set string = "A1,2,3,4,5"
set prefix = `echo $string | sed 's/^\([A-Z]\).*/\1/'`
echo $string | sed 's/,\([0-9]\)/,'$prefix'-\1/g'
Output is
A1,A-2,A-3,A-4,A-5
With
set string = "B-1,20,300"
Output is
B-1,B-20,B-300
Could you please try following(if ok with awk).
awk '
BEGIN{
FS=OFS=","
}
{
for(i=1;i<=NF;i++){
if($i !~ /^A/&&$i !~ /\"A/){
$i="A-"$i
}
}
}
1' Input_file
if your data in 'd' file, tried on gnu sed:
sed -E 'h;s/^(\w-).+/\1/;x;G;:s s/,([0-9]+)(.*\n(.+))/,\3\1\2/;ts; s/\n.+//' d
I am trying to extract a part of the filename - everything before the date and suffix. I am not sure the best way to do it in bashscript. Regex?
The names are part of the filename. I am trying to store it in a shellscript variable. The prefixes will not contain strange characters. The suffix will be the same. The files are stored in a directory - I will use loop to extract the portion of the filename for each file.
Expected input files:
EXAMPLE_FILE_2017-09-12.out
EXAMPLE_FILE_2_2017-10-12.out
Expected Extract:
EXAMPLE_FILE
EXAMPLE_FILE_2
Attempt:
filename=$(basename "$file")
folder=sed '^s/_[^_]*$//)' $filename
echo 'Filename:' $filename
echo 'Foldername:' $folder
$ cat file.txt
EXAMPLE_FILE_2017-09-12.out
EXAMPLE_FILE_2_2017-10-12.out
$
$ cat file.txt | sed 's/_[0-9]*-[0-9]*-[0-9]*\.out$//'
EXAMPLE_FILE
EXAMPLE_FILE_2
$
No need for useless use of cat, expensive forks and pipes. The shell can cut strings just fine:
$ file=EXAMPLE_FILE_2_2017-10-12.out
$ echo ${file%%_????-??-??.out}
EXAMPLE_FILE_2
Read all about how to use the %%, %, ## and # operators in your friendly shell manual.
Bash itself has regex capability so you do not need to run a utility. Example:
for fn in *.out; do
[[ $fn =~ ^(.*)_[[:digit:]]{4}-[[:digit:]]{2}-[[:digit:]]{2} ]]
cap="${BASH_REMATCH[1]}"
printf "%s => %s\n" "$fn" "$cap"
done
With the example files, output is:
EXAMPLE_FILE_2017-09-12.out => EXAMPLE_FILE
EXAMPLE_FILE_2_2017-10-12.out => EXAMPLE_FILE_2
Using Bash itself will be faster, more efficient than spawning sed, awk, etc for each file name.
Of course in use, you would want to test for a successful match:
for fn in *.out; do
if [[ $fn =~ ^(.*)_[[:digit:]]{4}-[[:digit:]]{2}-[[:digit:]]{2} ]]; then
cap="${BASH_REMATCH[1]}"
printf "%s => %s\n" "$fn" "$cap"
else
echo "$fn no match"
fi
done
As a side note, you can use Bash parameter expansion rather than a regex if you only need to trim the string after the last _ in the file name:
for fn in *.out; do
cap="${fn%_*}"
printf "%s => %s\n" "$fn" "$cap"
done
And then test $cap against $fn. If they are equal, the parameter expansion did not trim the file name after _ because it was not present.
The regex allows a test that a date-like string \d\d\d\d-\d\d-\d\d is after the _. Up to you which you need.
Code
See this code in use here
^\w+(?=_)
Results
Input
EXAMPLE_FILE_2017-09-12.out
EXAMPLE_FILE_2_2017-10-12.out
Output
EXAMPLE_FILE
EXAMPLE_FILE_2
Explanation
^ Assert position at start of line
\w+ Match any word character (a-zA-Z0-9_) between 1 and unlimited times
(?=_) Positive lookahead ensuring what follows is an underscore _ character
Simply with sed:
sed 's/_[^_]*$//' file
The output:
EXAMPLE_FILE
EXAMPLE_FILE_2
----------
In case of iterating through the list of files with extension .out - bash solution:
for f in *.out; do echo "${f%_*}"; done
awk -F_ 'NF-=1' OFS=_ file
EXAMPLE_FILE
EXAMPLE_FILE_2
Could you please try awk solution too, which will take care of all the .out files, note this has ben written and tested in GNU awk.
awk --re-interval 'FNR==1{if(val){close(val)};split(FILENAME, array,"_[0-9]{4}-[0-9]{2}-[0-9]{2}");print array[1];val=FILENAME;nextfile}' *.out
Also my awk version is old so I am using --re-interval, if you have latest version of awk you may need not to use it then.
Explanation and Non-one liner fom of solution: Adding a non-one liner form of solution too here with explanation.
awk --re-interval '##Using --re-interval for supporting ERE in my OLD awk version, if OP has new version of awk it could be removed.
FNR==1{ ##Checking here condition that when very first line of any Input_file is being read then do following actions.
if(val){ ##Checking here if variable named val value is NOT NULL then do following.
close(val) ##close the Input_file named which is stored in variable val, so that we will NOT face problem of TOO MANY FILES OPENED, so it will be like one file read close it in background then.
};
split(FILENAME, array,"_[0-9]{4}-[0-9]{2}-[0-9]{2}");##Splitting FILENAME(which will have Input_file name in it) into array named array only, whose separator is a 4 digits-2 digits- then 2 digits, actually this will take care of YYYY-MM-DD format in Input_file(s) and it will be easier for us to get the file name part.
print array[1]; ##Printing array 1st element here.
val=FILENAME; ##Storing FILENAME variable value which will have current Input_file name in it to variable named val, so that we could close it in background.
nextfile ##nextfile as it name suggests it will skip all the lines in current line and jump onto the next file to save some cpu cycles of our system.
}
' *.out ##Mentioning all *.out Input_file(s) here.
Consider the following:
var="text more text and yet more text"
echo $var | egrep "yet more (text)"
It should be possible to get the result of the regex as the string: text
However, I don't see any way to do this in bash with grep or its siblings at the moment.
In perl, php or similar regex engines:
$output = preg_match('/yet more (text)/', 'text more text yet more text');
$output[1] == "text";
Edit: To elaborate why I can't just multiple-regex, in the end I will have a regex with multiple of these (Pictured below) so I need to be able to get all of them. This also eliminates the option of using lookahead/lookbehind (As they are all variable length)
egrep -i "([0-9]+) +$USER +([0-9]+).+?(/tmp/Flash[0-9a-z]+) "
Example input as requested, straight from lsof (Replace $USER with "j" for this input data):
npviewer. 17875 j 11u REG 8,8 59737848 524264 /tmp/FlashXXu8pvMg (deleted)
npviewer. 17875 j 17u REG 8,8 16037387 524273 /tmp/FlashXXIBH29F (deleted)
The end goal is to cp /proc/$var1/fd/$var2 ~/$var3 for every line, which ends up "Downloading" flash files (Flash used to store in /tmp but they drm'd it up)
So far I've got:
#!/bin/bash
regex="([0-9]+) +j +([0-9]+).+?/tmp/(Flash[0-9a-zA-Z]+)"
echo "npviewer. 17875 j 11u REG 8,8 59737848 524264 /tmp/FlashXXYOvS8S (deleted)" |
sed -r -n -e " s%^.*?$regex.*?\$%\1 \2 \3%p " |
while read -a array
do
echo /proc/${array[0]}/fd/${array[1]} ~/${array[2]}
done
It cuts off the first digits of the first value to return, and I'm not familiar enough with sed to see what's wrong.
End result for downloading flash 10.2+ videos (Including, perhaps, encrypted ones):
#!/bin/bash
lsof | grep "/tmp/Flash" | sed -r -n -e " s%^.+? ([0-9]+) +$USER +([0-9]+).+?/tmp/(Flash[0-9a-zA-Z]+).*?\$%\1 \2 \3%p " |
while read -a array
do
cp /proc/${array[0]}/fd/${array[1]} ~/${array[2]}
done
Edit: look at my other answer for a simpler bash-only solution.
So, here the solution using sed to fetch the right groups and split them up. You later still have to use bash to read them. (And in this way it only works if the groups themselves do not contain any spaces - otherwise we had to use another divider character and patch read by setting $IFS to this value.)
#!/bin/bash
USER=j
regex=" ([0-9]+) +$USER +([0-9]+).+(/tmp/Flash[0-9a-zA-Z]+) "
sed -r -n -e " s%^.*$regex.*\$%\1 \2 \3%p " |
while read -a array
do
cp /proc/${array[0]}/fd/${array[1]} ~/${array[2]}
done
Note that I had to adapt your last regex group to allow uppercase letters, and added a space at the beginning to be sure to capture the whole block of numbers. Alternatively here a \b (word limit) would have worked, too.
Ah, I forget mentioning that you should pipe the text to this script, like this:
./grep-result.sh < grep-result-test.txt
(provided your files are named like this). Instead you can add a < grep-result-test after the sed call (before the |), or prepend the line with cat grep-result-test.txt |.
How does it work?
sed -r -n calls sed in extended-regexp-mode, and without printing anything automatically.
-e " s%^.*$regex.*\$%\1 \2 \3%p " gives the sed program, which consists of a single s command.
I'm using % instead of the normal / as parameter separator, since / appears inside the regex and I don't want to escape it.
The regex to search is prefixed by ^.* and suffixed by .*$ to grab the whole line (and avoid printing parts of the rest of the line).
Note that this .* grabs greedy, so we have to insert a space into our regexp to avoid it grabbing the start of the first digit group too.
The replacement text contains of the three parenthesed groups, separated by spaces.
the p flag at the end of the command says to print out the pattern space after replacement. Since we grabbed the whole line, the pattern space consists of only the replacement text.
So, the output of sed for your example input is this:
5 11 /tmp/FlashXXu8pvMg
5 17 /tmp/FlashXXIBH29F
This is much more friendly for reuse, obviously.
Now we pipe this output as input to the while loop.
read -a array reads a line from standard input (which is the output from sed, due to our pipe), splits it into words (at spaces, tabs and newlines), and puts the words into an array variable.
We could also have written read var1 var2 var3 instead (preferably using better variable names), then the first two words would be put to $var1 and $var2, with $var3 getting the rest.
If read succeeded reading a line (i.e. not end-of-file), the body of the loop is executed:
${array[0]} is expanded to the first element of the array and similarly.
When the input ends, the loop ends, too.
This isn't possible using grep or another tool called from a shell prompt/script because a child process can't modify the environment of its parent process. If you're using bash 3.0 or better, then you can use in-process regular expressions. The syntax is perl-ish (=~) and the match groups are available via $BASH_REMATCH[x], where x is the match group.
After creating my sed-solution, I also wanted to try the pure-bash approach suggested by Mark. It works quite fine, for me.
#!/bin/bash
USER=j
regex=" ([0-9]+) +$USER +([0-9]+).+(/tmp/Flash[0-9a-zA-Z]+) "
while read
do
if [[ $REPLY =~ $regex ]]
then
echo cp /proc/${BASH_REMATCH[1]}/fd/${BASH_REMATCH[2]} ~/${BASH_REMATCH[3]}
fi
done
(If you upvote this, you should think about also upvoting Marks answer, since it is essentially his idea.)
The same as before: pipe the text to be filtered to this script.
How does it work?
As said by Mark, the [[ ... ]] special conditional construct supports the binary operator =~, which interprets his right operand (after parameter expansion) as a extended regular expression (just as we want), and matches the left operand against this. (We have again added a space at front to avoid matching only the last digit.)
When the regex matches, the [[ ... ]] returns 0 (= true), and also puts the parts matched by the individual groups (and the whole expression) into the array variable BASH_REMATCH.
Thus, when the regex matches, we enter the then block, and execute the commands there.
Here again ${BASH_REMATCH[1]} is an array-access to an element of the array, which corresponds to the first matched group. ([0] would be the whole string.)
Another note: Both my scripts accept multi-line input and work on every line which matches. Non-matching lines are simply ignored. If you are inputting only one line, you don't need the loop, a simple if read ; then ... or even read && [[ $REPLY =~ $regex ]] && ... would be enough.
echo "$var" | pcregrep -o "(?<=yet more )text"
Well, for your simple example, you can do this:
var="text more text and yet more text"
echo $var | grep -e "yet more text" | grep -o "text"
How do I remove duplicate characters and keep the unique one only.
For example, my input is:
EFUAHUU
UUUEUUUUH
UJUJHHACDEFUCU
Expected output is:
EFUAH
UEH
UJHACDEF
I came across perl -pe's/$1//g while/(.).*\/' which is wonderful but it is removing even the single occurrence of the character in output.
This can be done using positive lookahead :
perl -pe 's/(.)(?=.*?\1)//g' FILE_NAME
The regex used is: (.)(?=.*?\1)
. : to match any char.
first () : remember the matched
single char.
(?=...) : +ve lookahead
.*? : to match anything in between
\1 : the remembered match.
(.)(?=.*?\1) : match and remember
any char only if it appears again
later in the string.
s/// : Perl way of doing the
substitution.
g: to do the substitution
globally...that is don't stop after
first substitution.
s/(.)(?=.*?\1)//g : this will
delete a char from the input string
only if that char appears again later
in the string.
This will not maintain the order of the char in the input because for every unique char in the input string, we retain its last occurrence and not the first.
To keep the relative order intact we can do what KennyTM tells in one of the comments:
reverse the input line
do the substitution as before
reverse the result before printing
The Perl one line for this is:
perl -ne '$_=reverse;s/(.)(?=.*?\1)//g;print scalar reverse;' FILE_NAME
Since we are doing print manually after reversal, we don't use the -p flag but use the -n flag.
I'm not sure if this is the best one-liner to do this. I welcome others to edit this answer if they have a better alternative.
if Perl is not a must, you can also use awk. here's a fun benchmark on the Perl one liners posted against awk. awk is 10+ seconds faster for a file with 3million++ lines
$ wc -l <file2
3210220
$ time awk 'BEGIN{FS=""}{delete _;for(i=1;i<=NF;i++){if(!_[$i]++) printf $i};print""}' file2 >/dev/null
real 1m1.761s
user 0m58.565s
sys 0m1.568s
$ time perl -n -e '%seen=();' -e 'for (split //) {print unless $seen{$_}++;}' file2 > /dev/null
real 1m32.123s
user 1m23.623s
sys 0m3.450s
$ time perl -ne '$_=reverse;s/(.)(?=.*?\1)//g;print scalar reverse;' file2 >/dev/null
real 1m17.818s
user 1m10.611s
sys 0m2.557s
$ time perl -ne'my%s;print grep!$s{$_}++,split//' file2 >/dev/null
real 1m20.347s
user 1m13.069s
sys 0m2.896s
perl -ne'my%s;print grep!$s{$_}++,split//'
Here is a solution, that I think should work faster than the lookahead one, but is not regexp-based and uses hashtable.
perl -n -e '%seen=();' -e 'for (split //) {print unless $seen{$_}++;}'
It splits every line into characters and prints only the first appearance by counting appearances inside %seen hashtable
Tie::IxHash is a good module to store hash order (but may be slow, you will need to benchmark if speed is important). Example with tests:
use Test::More 0.88;
use Tie::IxHash;
sub dedupe {
my $str=shift;
my $hash=Tie::IxHash->new(map { $_ => 1} split //,$str);
return join('',$hash->Keys);
}
{
my $str='EFUAHUU';
is(dedupe($str),'EFUAH');
}
{
my $str='EFUAHHUU';
is(dedupe($str),'EFUAH');
}
{
my $str='UJUJHHACDEFUCU';
is(dedupe($str),'UJHACDEF');
}
done_testing();
Use uniq from List::MoreUtils:
perl -MList::MoreUtils=uniq -ne 'print uniq split ""'
If the set of characters that can be encountered is restricted, e.g. only letters, then the easiest solution will be with tr
perl -p -e 'tr/a-zA-Z/a-zA-Z/s'
It will replace all the letters by themselves, leaving other characters unaffected and /s modifier will squeeze repeated occurrences of the same character (after replacement), thus removing duplicates
Me bad - it removes only adjoining appearances. Disregard
This looks like a classic application of positive lookbehind, but unfortunately perl doesn't support that. In fact, doing this (matching the preceding text of a character in a string with a full regex whose length is indeterminable) can only be done with .NET regex classes, I think.
However, positive lookahead supports full regexes, so all you need to do is reverse the string, apply positive lookahead (like unicornaddict said):
perl -pe 's/(.)(?=.*?\1)//g'
And reverse it back, because without the reverse that'll only keep the duplicate character at the last place in a line.
MASSIVE EDIT
I've been spending the last half an hour on this, and this looks like this works, without the reversing.
perl -pe 's/\G$1//g while (/(.).*(?=\1)/g)' FILE_NAME
I don't know whether to be proud or horrified. I'm basically doing the positive looakahead, then substituting on the string with \G specified - which makes the regex engine start its matching from the last place matched (internally represented by the pos() variable).
With test input like this:
aabbbcbbccbabb
EFAUUUUH
ABCBBBBD
DEEEFEGGH
AABBCC
The output is like this:
abc
EFAUH
ABCD
DEFGH
ABC
I think it's working...
Explanation - Okay, in case my explanation last time wasn't clear enough - the lookahead will go and stop at the last match of a duplicate variable [in the code you can do a print pos(); inside the loop to check] and the s/\G//g will remove it [you don't need the /g really]. So within the loop, the substitution will continue removing until all such duplicates are zapped. Of course, this might be a little too processor intensive for your tastes... but so are most of the regex-based solutions you'll see. The reversing/lookahead method will probably be more efficient than this, though.
From the shell, this works:
sed -e 's/$/<EOL>/ ; s/./&\n/g' test.txt | uniq | sed -e :a -e '$!N; s/\n//; ta ; s/<EOL>/\n/g'
In words: mark every linebreak with a <EOL> string, then put every character on a line of its own, then use uniq to remove duplicate lines, then strip out all the linebreaks, then put back linebreaks instead of the <EOL> markers.
I found the -e :a -e '$!N; s/\n//; ta part in a forum post and I don't understand the seperate -e :a part, or the $!N part, so if anyone can explain those, I'd be grateful.
Hmm, that one does only consecutive duplicates; to eliminate all duplicates you could do this:
cat test.txt | while read line ; do echo $line | sed -e 's/./&\n/g' | sort | uniq | sed -e :a -e '$!N; s/\n//; ta' ; done
That puts the characters in each line in alphabetical order though.
use strict;
use warnings;
my ($uniq, $seq, #result);
$uniq ='';
sub uniq {
$seq = shift;
for (split'',$seq) {
$uniq .=$_ unless $uniq =~ /$_/;
}
push #result,$uniq;
$uniq='';
}
while(<DATA>){
uniq($_);
}
print #result;
__DATA__
EFUAHUU
UUUEUUUUH
UJUJHHACDEFUCU
The output:
EFUAH
UEH
UJHACDEF
for a file containing the data you list named foo.txt
python -c "print set(open('foo.txt').read())"
I see lots of examples and man pages on how to do things like search-and-replace using sed, awk, or gawk.
But in my case, I have a regular expression that I want to run against a text file to extract a specific value. I don't want to do search-and-replace. This is being called from bash. Let's use an example:
Example regular expression:
.*abc([0-9]+)xyz.*
Example input file:
a
b
c
abc12345xyz
a
b
c
As simple as this sounds, I cannot figure out how to call sed/awk/gawk correctly. What I was hoping to do, is from within my bash script have:
myvalue=$( sed <...something...> input.txt )
Things I've tried include:
sed -e 's/.*([0-9]).*/\\1/g' example.txt # extracts the entire input file
sed -n 's/.*([0-9]).*/\\1/g' example.txt # extracts nothing
My sed (Mac OS X) didn't work with +. I tried * instead and I added p tag for printing match:
sed -n 's/^.*abc\([0-9]*\)xyz.*$/\1/p' example.txt
For matching at least one numeric character without +, I would use:
sed -n 's/^.*abc\([0-9][0-9]*\)xyz.*$/\1/p' example.txt
You can use sed to do this
sed -rn 's/.*abc([0-9]+)xyz.*/\1/gp'
-n don't print the resulting line
-r this makes it so you don't have the escape the capture group parens().
\1 the capture group match
/g global match
/p print the result
I wrote a tool for myself that makes this easier
rip 'abc(\d+)xyz' '$1'
I use perl to make this easier for myself. e.g.
perl -ne 'print $1 if /.*abc([0-9]+)xyz.*/'
This runs Perl, the -n option instructs Perl to read in one line at a time from STDIN and execute the code. The -e option specifies the instruction to run.
The instruction runs a regexp on the line read, and if it matches prints out the contents of the first set of bracks ($1).
You can do this will multiple file names on the end also. e.g.
perl -ne 'print $1 if /.*abc([0-9]+)xyz.*/' example1.txt example2.txt
If your version of grep supports it you could use the -o option to print only the portion of any line that matches your regexp.
If not then here's the best sed I could come up with:
sed -e '/[0-9]/!d' -e 's/^[^0-9]*//' -e 's/[^0-9]*$//'
... which deletes/skips with no digits and, for the remaining lines, removes all leading and trailing non-digit characters. (I'm only guessing that your intention is to extract the number from each line that contains one).
The problem with something like:
sed -e 's/.*\([0-9]*\).*/&/'
.... or
sed -e 's/.*\([0-9]*\).*/\1/'
... is that sed only supports "greedy" match ... so the first .* will match the rest of the line. Unless we can use a negated character class to achieve a non-greedy match ... or a version of sed with Perl-compatible or other extensions to its regexes, we can't extract a precise pattern match from with the pattern space (a line).
You can use awk with match() to access the captured group:
$ awk 'match($0, /abc([0-9]+)xyz/, matches) {print matches[1]}' file
12345
This tries to match the pattern abc[0-9]+xyz. If it does so, it stores its slices in the array matches, whose first item is the block [0-9]+. Since match() returns the character position, or index, of where that substring begins (1, if it starts at the beginning of string), it triggers the print action.
With grep you can use a look-behind and look-ahead:
$ grep -oP '(?<=abc)[0-9]+(?=xyz)' file
12345
$ grep -oP 'abc\K[0-9]+(?=xyz)' file
12345
This checks the pattern [0-9]+ when it occurs within abc and xyz and just prints the digits.
perl is the cleanest syntax, but if you don't have perl (not always there, I understand), then the only way to use gawk and components of a regex is to use the gensub feature.
gawk '/abc[0-9]+xyz/ { print gensub(/.*([0-9]+).*/,"\\1","g"); }' < file
output of the sample input file will be
12345
Note: gensub replaces the entire regex (between the //), so you need to put the .* before and after the ([0-9]+) to get rid of text before and after the number in the substitution.
If you want to select lines then strip out the bits you don't want:
egrep 'abc[0-9]+xyz' inputFile | sed -e 's/^.*abc//' -e 's/xyz.*$//'
It basically selects the lines you want with egrep and then uses sed to strip off the bits before and after the number.
You can see this in action here:
pax> echo 'a
b
c
abc12345xyz
a
b
c' | egrep 'abc[0-9]+xyz' | sed -e 's/^.*abc//' -e 's/xyz.*$//'
12345
pax>
Update: obviously if you actual situation is more complex, the REs will need to me modified. For example if you always had a single number buried within zero or more non-numerics at the start and end:
egrep '[^0-9]*[0-9]+[^0-9]*$' inputFile | sed -e 's/^[^0-9]*//' -e 's/[^0-9]*$//'
The OP's case doesn't specify that there can be multiple matches on a single line, but for the Google traffic, I'll add an example for that too.
Since the OP's need is to extract a group from a pattern, using grep -o will require 2 passes. But, I still find this the most intuitive way to get the job done.
$ cat > example.txt <<TXT
a
b
c
abc12345xyz
a
abc23451xyz asdf abc34512xyz
c
TXT
$ cat example.txt | grep -oE 'abc([0-9]+)xyz'
abc12345xyz
abc23451xyz
abc34512xyz
$ cat example.txt | grep -oE 'abc([0-9]+)xyz' | grep -oE '[0-9]+'
12345
23451
34512
Since processor time is basically free but human readability is priceless, I tend to refactor my code based on the question, "a year from now, what am I going to think this does?" In fact, for code that I intend to share publicly or with my team, I'll even open man grep to figure out what the long options are and substitute those. Like so: grep --only-matching --extended-regexp
why even need match group
gawk/mawk/mawk2 'BEGIN{ FS="(^.*abc|xyz.*$)" } ($2 ~ /^[0-9]+$/) {print $2}'
Let FS collect away both ends of the line.
If $2, the leftover not swallowed by FS, doesn't contain non-numeric characters, that's your answer to print out.
If you're extra cautious, confirm length of $1 and $3 both being zero.
** edited answer after realizing zero length $2 will trip up my previous solution
there's a standard piece of code from awk channel called "FindAllMatches" but it's still very manual, literally, just long loops of while(), match(), substr(), more substr(), then rinse and repeat.
If you're looking for ideas on how to obtain just the matched pieces, but upon a complex regex that matches multiple times each line, or none at all, try this :
mawk/mawk2/gawk 'BEGIN { srand(); for(x = 0; x < 128; x++ ) {
alnumstr = sprintf("%s%c", alnumstr , x)
};
gsub(/[^[:alnum:]_=]+|[AEIOUaeiou]+/, "", alnumstr)
# resulting str should be 44-chars long :
# all digits, non-vowels, equal sign =, and underscore _
x = 10; do { nonceFS = nonceFS substr(alnumstr, 1 + int(44*rand()), 1)
} while ( --x ); # you can pick any level of precision you need.
# 10 chars randomly among the set is approx. 54-bits
#
# i prefer this set over all ASCII being these
# just about never require escaping
# feel free to skip the _ or = or r/t/b/v/f/0 if you're concerned.
#
# now you've made a random nonce that can be
# inserted right in the middle of just about ANYTHING
# -- ASCII, Unicode, binary data -- (1) which will always fully
# print out, (2) has extremely low chance of actually
# appearing inside any real word data, and (3) even lower chance
# it accidentally alters the meaning of the underlying data.
# (so intentionally leaving them in there and
# passing it along unix pipes remains quite harmless)
#
# this is essentially the lazy man's approach to making nonces
# that kinda-sorta have some resemblance to base64
# encoded, without having to write such a module (unless u have
# one for awk handy)
regex1 = (..); # build whatever regex you want here
FS = OFS = nonceFS;
} $0 ~ regex1 {
gsub(regex1, nonceFS "&" nonceFS); $0 = $0;
# now you've essentially replicated what gawk patsplit( ) does,
# or gawk's split(..., seps) tracking 2 arrays one for the data
# in between, and one for the seps.
#
# via this method, that can all be done upon the entire $0,
# without any of the hassle (and slow downs) of
# reading from associatively-hashed arrays,
#
# simply print out all your even numbered columns
# those will be the parts of "just the match"
if you also run another OFS = ""; $1 = $1; , now instead of needing 4-argument split() or patsplit(), both of which being gawk specific to see what the regex seps were, now the entire $0's fields are in data1-sep1-data2-sep2-.... pattern, ..... all while $0 will look EXACTLY the same as when you first read in the line. a straight up print will be byte-for-byte identical to immediately printing upon reading.
Once i tested it to the extreme using a regex that represents valid UTF8 characters on this. Took maybe 30 seconds or so for mawk2 to process a 167MB text file with plenty of CJK unicode all over, all read in at once into $0, and crank this split logic, resulting in NF of around 175,000,000, and each field being 1-single character of either ASCII or multi-byte UTF8 Unicode.
you can do it with the shell
while read -r line
do
case "$line" in
*abc*[0-9]*xyz* )
t="${line##abc}"
echo "num is ${t%%xyz}";;
esac
done <"file"
For awk. I would use the following script:
/.*abc([0-9]+)xyz.*/ {
print $0;
next;
}
{
/* default, do nothing */
}
gawk '/.*abc([0-9]+)xyz.*/' file