I'm trying to extract a tag value of an HTML node that I already have in a variable.
I'm currently using Zsh but I'm trying to make it work in Bash as well.
The current variable has the value:
<span class="alter" fill="#ffedf0" data-count="0" data-more="none"/>
and I would like to get the value of data-count (in this case 0, but could be any length integer).
I have tried using cut, sed and the variables expansion as explained in this question but I haven't managed to adapt the regexs, or maybe it has to be done differently for Zsh.
There is no reason why sed would not work in this situation. For your specific case, I would do something like this:
sed 's/.*data-count="\([0-9]*\)".*/\1/g' file_name.txt
Basically, it just states that sed is looking for the a pattern that contains data-count=, then saves everything within the paranthesis \(...\) into \1, which is subsequently printed in place of the match (full line due to the .*)
Could you please try following.
awk 'match($0,/data-count=[^ ]*/){print substr($0,RSTART+12,RLENGTH-13)}' Input_file
Explanation: Using match function of awk to match regex data-count=[^ ]* means match everything from data-count till a space comes, if this regex is TRUE(a match is found) then out of the box variables RSTART and RLENGTH will be set. Later I am printing current line's sub-string as per these variables values to get only value of data-count.
With sed could you please try following.
sed 's/.*data-count=\"\([^"]*\).*/\1/' Input_file
Explanation: Using sed's capability of group referencing and saving regex value in first group after data-count=\" which is its length, then since using s(substitution) with sed so mentioning 1 will replace all with \1(which is matched regex value in temporary memory, group referencing).
As was said before, to be on the safe side and handle any syntactically valid HTML tag, a parser would be strongly advised. But if you know in advance, what the general format of your HTML element will look like, the following hack might come handy:
Assume that your variable is called "html"
html='<span class="alter" fill="#ffedf0" data-count="0" data-more="none"/>'
First adapt it a bit:
htmlx="tag ${html%??}"
This will add the string tag in front and remove the final />
Now make an associative array:
declare -A fields
fields=( ${=$(tr = ' ' <<<$htmlx)} )
The tr turns the equal sign into a space and the ${= handles word splitting. You can now access the values of your attributes by, say,
echo $fields[data-count]
Note that this still has the surrounding double quotes. Yuo can easily remove them by
echo ${${fields[data-count]%?}#?}
Of course, once you do this hack, you have access to all attributes in the same way.
Related
Suppose there's a text file with the following line:
export MYSQL_ADMIN=''
I want to insert text inside that single quote using the sed command, so that it changes to something like this for example:
export MYSQL_ADMIN='abc1'
What is the appropriate sed command for that in Linux?
I tried
sed -i -e ''/MYSQL_ADMIN/s/''/'abc1'/g"
but it didn't work.
Something like sed -i "s;export MYSQL_ADMIN=.*;export MYSQL_ADMIN='abc1';" /path/to/file.ext
-i modify file in place
s means substitute,
First block is what you are matching as an regular expression - the .* matches everything to the end of the line, this ensures you don't keep any text on that line after the substitue - and second block is what you are replacing with that match.
Always check the file after each run of sed if there is no error and check what changed.
To get the single quotes to print you may have to do ""'"" like ""'""abc1""'""
It is important to understand that although
I want to insert text inside that single quote using the sed command
is a perfectly good characterization of the effect you want to achieve, it does not map directly onto operations from sed's repertoire. With sed, the appropriate tool for most line modifications is the s command, which substitutes specified text for one or more matches to a specified regular expression. That would be the most natural thing to use for your case.
Additionally, it is important with sed to understand how and when to bind commands to specific lines. If you don't do that for a given command then it is applied to all lines. Sometimes that's fine, but other times it will produce unwanted results.
I tried
sed -i -e ''/MYSQL_ADMIN/s/''/'abc1'/g"
but it didn't work.
The two leading single quotes in that sed expression match each other, leaving the trailing double quote unmatched. Also, you do not specify the name of the file to modify. This variation would at least be valid shell syntax, and it would have the desired effect on the specified line appearing in file my_script:
sed -i -e "/MYSQL_ADMIN/s/''/'abc1'/g" my_script
That might also make other, unwanted changes, however.
You need to make some assumptions about the content of the file in order to do such a thing at all. The above depends on the text MYSQL_ADMIN and '' to appear on the same line only in the line(s) you want to modify. That may turn out to hold, but it seems unnecessarily risky. An assumption more likely to hold in general would be that there will be only one assignment to variable MYSQL_ADMIN, or that it is acceptable to modify all such assignments that assign a single-quote-delimited empty value.
Going with the latter, one might end up with this:
sed -i -e "s/\<MYSQL_ADMIN=''\(\s\|$\)/MYSQL_ADMIN='abc1'\1/g" my_script
The pattern \<MYSQL_ADMIN=''\(\s\|$\) improves on your plain MYSQL_ADMIN in these significant ways:
the \< causes it to match only immediately after a word boundary -- start of line, whitesepace, or punctuation. This prevents substitutions for other variables whose names happen to end with MYSQL_ADMIN. If you prefer, it would be even stronger to instead anchor the match to the beginning of the line with ^.
including the ='' in the pattern distinguishes between MYSQL_ADMIN and variables whose names contain that as an initial substring. It also ensures that the '' that gets replaced, if any, goes with the variable and does not merely appear somewhere else on the line.
the \(\s\|$\) both matches and captures either a whitespace character or the empty string at the end of a line. This distinguishes between assignments of an empty value and assignments of values that are merely prefixed by '' (which is valid if the file is a shell script). Having included it in the match, the capture allows the matched text, if any, to be preserved in the output (via the \1 in the replacement).
Because that matches the whole assignment, a complete assignment must appear in the replacement, too. On the other hand, this means that (probably) you can apply the command to every line, as shown, with no particular loss of efficiency relative to the previous command.
Even that might produce changes you didn't want, however, such as in comment lines or quoted text.
I am trying to use sed to print the contents between two patterns including the first one. I was using this answer as a source.
My file looks like this:
>item_1
abcabcabacabcabcabcabcabacabcabcabcabcabacabcabc
>item_2
bcdbcdbcdbcdbbcdbcdbcdbcdbbcdbcdbcdbcdbbcdbcdbcdbcdbbcdbcdbcdbcdb
>item_3
cdecde
>item_4
defdefdefdefdefdefdef
I want it to start searching from item_2 (and include) and finish at next occuring > (not include). So my code is sed -n '/item_2/,/>/{/>/!p;}'.
The result wanted is:
item_2
bcdbcdbcdbcdbbcdbcdbcdbcdbbcdbcdbcdbcdbbcdbcdbcdbcdbbcdbcdbcdbcdb
but I get it without item_2.
Any ideas?
Using awk, split input by >s and print part(s) matching item_2.
$ awk 'BEGIN{RS=">";ORS=""} /item_2/' file
item_2
bcdbcdbcdbcdbbcdbcdbcdbcdbbcdbcdbcdbcdbbcdbcdbcdbcdbbcdbcdbcdbcdb
I would go for the awk method suggested by oguz for its simplicity. Now if you are interested in a sed way, out of curiosity, you could fix what you have already tried with a minor change :
sed -n '/^>item_2/ s/.// ; //,/>/ { />/! p }' input_file
The empty regex // recalls the previous regex, which is handy here to avoid duplicating /item_2/. But keep in mind that // is actually dynamic, it recalls the latest regex evaluated at runtime, which is not necessarily the closest regex on its left (although it's often the case). Depending on the program flow (branching, address range), the content of the same // can change and... actually here we have an interesting example ! (and I'm not saying that because it's my baby ^^)
On a line where /^>item_2/ matches, the s/.// command is executed and the latest regex before // becomes /./, so the following address range is equivalent to /./,/>/.
On a line where /^>item_2/ does not match, the latest regex before // is /^>item_2/ so the range is equivalent to /^>item_2/,/>/.
To avoid confusion here as the effect of // changes during execution, it's important to note that an address range evaluates only its left side when not triggered and only its right side when triggered.
This might work for you (GNU sed):
sed -n ':a;/^>item_2/{s/.//;:b;p;n;/^>/!bb;ba}' file
Turn off implicit printing -n.
If a line begins >item_2, remove the first character, print the line and fetch the next line
If that line does not begins with a >, repeat the last two instructions.
Otherwise, repeat the whole set of instructions.
If there will always be only one line following >item_2, then:
sed '/^>item_2/!d;s/.//;n' file
I'm looking for a one liner to replace any character in a variable string at a variable position with a variable substitute. I came up with this working solution:
echo "$string" | sed "s/./${replacement}/${position}"
An example usage:
string=aaaaa
replacement=b
position=3
echo "$string" | sed "s/./${replacement}/${position}"
aabaa
Unfortunately, when I run shellcheck with a script which contains my current solution it tells me:
SC2001: See if you can use ${variable//search/replace} instead.
I'd like to use parameter expansion like it's suggesting instead of piping to sed, but I'm unclear as to the proper formatting when using a position variable. The official documentation doesn't seem to discuss positioning within strings at all.
Is this possible?
Bash doesn't have a general-case replacement for all sed facilities (the shellcheck wiki page for warning SC2001 acknowledges as much), but in some specific scenarios -- including the case posed -- parameter expansions can be combined to achieve the desired effect:
string=aaaaa
replacement=b
position=3
echo "${string:0:$(( position - 1 ))}${replacement}${string:position}"
Here, we're splitting the value up into substrings: ${string:0:$(( position - 1 ))} is the text preceding the content to be replaced, and ${string:position} is the text following that point.
I have a simple sed script and I am replacing a bunch of lines in my application dynamically with a variable, the variable is a list of strings.My function works but does not keep the original indentation.the function deletes the line if it contains the certain string and replaces the line with a completely new line, I could not do a replace due to certain syntax restrictions.
How do I keep my original indentation when the line is replaced
Can I capitalize my variable and remove the underscore on the fly, i.e. the title is a capitalize and underscore removed version of the variableName, the list of items in the variable array is really long so I am trying to do this in one shot.
Ex: I want report_type -> Report Type done mid process
Is there a better way to solve this with sed? Thanks for any inputs much appreciated.
sed function is as follows
variableName=$1
sed -i "/name\=\"${variableName}\.name\" value\=model\.${variableName}\.name options\=\#lists\./c\\{\{\> \_dropdown title\=\"${variableName}\" required\=true name\=\"${variableName}\"\}\}" test
SAMPLE INPUT
{{> _select title="Report Type" required=true name="report_type.name" value=model.report_type.name options=#lists.report_type}}
SAMPLE EXPECTED OUPUT
{{> _dropdown title="Report Type" required=true name="report_type" value=model.report_type.name}}
sample input variable
report_type
Try this:
sed -E "s/^(\s+).*name\=\"(report_type)\.name\" value\=model\.report_type\.name options\=\#lists\..*$/\1\{\{\> \_dropdown title\=\"\2\" required\=true name\=\"\2\"\}\}/;T;s/\"(\w+)_(\w+)\"/\"\u\1 \u\2\"/g" input.txt > output.txt
I used "report_type" instead of ${variableName} for testing as an sed one-liner.
Please change back to ${variableName}.
Then go back to using -i (in addition to -E, which is for extended regex).
I am not sure whether I can do it without extended regex, let me know if that is necessary.
use s/// to replace fine tuned line
first capture group for the white space making the indentation
second capture group for the variable name
stop if that did not replace anything, T;
another s///
look for something consisting of only letters between "",
with a "_" between two parts,
seems safe enough because this step is only done on the already replaced line
replace by two parts, without "_"
\u for making camel case
Note:
Doing this on your sample input creates two very similar lines.
I assume that is intentional. Otherwise please provide desired output.
Using GNU sed version 4.2.1.
Interesting line of output:
{{> _dropdown title="Report Type" required=true name="Report Type"}}
I am writing a shell (bash) script and I'm trying to figure out an easy way to accomplish a simple task.
I have some string in a variable.
I don't know if this is relevant, but it can contain spaces, newlines, because actually this string is the content of a whole text file.
I want to replace the last occurence of a certain substring with something else.
Perhaps I could use a regexp for that, but there are two moments that confuse me:
I need to match from the end, not from the start
the substring that I want to scan for is fixed, not variable.
for truncating at the start: ${var#pattern}
truncating at the end ${var%pattern}
${var/pattern/repl} for general replacement
the patterns are 'filename' style expansion, and the last one can be prefixed with # or % to match only at the start or end (respectively)
it's all in the (long) bash manpage. check the "Parameter Expansion" chapter.
amn expression like this
s/match string here$/new string/
should do the trick - s is for sustitute, / break up the command, and the $ is the end of line marker. You can try this in vi to see if it does what you need.
I would look up the man pages for awk or sed.
Javier's answer is shell specific and won't work in all shells.
The sed answers that MrTelly and epochwolf alluded to are incomplete and should look something like this:
MyString="stuff ttto be edittted"
NewString=`echo $MyString | sed -e 's/\(.*\)ttt\(.*\)/\1xxx\2/'`
The reason this works without having to use the $ to mark the end is that the first '.*' is greedy and will attempt to gather up as much as possible while allowing the rest of the regular expression to be true.
This sed command should work fine in any shell context used.
Usually when I get stuck with Sed I use this page,
http://sed.sourceforge.net/sed1line.txt