From c07a5a71e2aedd0318ab34be1f0c7ac28de101fb Mon Sep 17 00:00:00 2001
From: John Kerl <kerl@fb.com>
Date: Sat, 8 Dec 2018 21:44:50 -0500
Subject: [PATCH] close https://github.com/johnkerl/miller/issues/203

---
 doc/content-for-faq.html | 14 ++++++++++++++
 doc/data/question.dat    |  1 +
 doc/faq.html             | 40 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+)
 create mode 100644 doc/data/question.dat

diff --git a/doc/content-for-faq.html b/doc/content-for-faq.html
index b76dc6e5b..03c9cfe52 100644
--- a/doc/content-for-faq.html
+++ b/doc/content-for-faq.html
@@ -154,6 +154,20 @@ POKI_RUN_COMMAND{{echo x,y,z | mlr --csv --implicit-csv-header reorder -f 3,1,2}
 
 POKI_RUN_COMMAND{{echo 'x.a=3,y:b=4,z/c=5' | mlr put '${product.all} = ${x.a} * ${y:b} * ${z/c}'}}HERE
 
+</div>
+<h1>How to escape '?' in regexes?</h1>
+<button style="font-weight:bold;color:maroon;border:0" padding=0 onclick="toggle_by_name('section_toggle_escape_in_regex');" href="javascript:;">Toggle section visibility</button>
+<div id="section_toggle_escape_in_regex" style="display: block">
+
+<p/> One way is to use square brackets; an alternative is to use simple
+string-substitution rather than a regular expression.
+
+POKI_RUN_COMMAND{{cat data/question.dat}}HERE
+POKI_RUN_COMMAND{{mlr --oxtab put '$c = gsub($a, "[?]"," ...")' data/question.dat}}HERE
+POKI_RUN_COMMAND{{mlr --oxtab put '$c = ssub($a, "?"," ...")' data/question.dat}}HERE
+
+<p/> The <tt>ssub</tt> function exists precisely for this reason: so you don&rsquo;t have to escape anything.
+
 </div>
 <h1>How can I put single-quotes into strings?</h1>
 <button style="font-weight:bold;color:maroon;border:0" padding=0 onclick="toggle_by_name('section_toggle_single_quotes_in_strings');" href="javascript:;">Toggle section visibility</button>
diff --git a/doc/data/question.dat b/doc/data/question.dat
new file mode 100644
index 000000000..d40b0adfd
--- /dev/null
+++ b/doc/data/question.dat
@@ -0,0 +1 @@
+a=is it?,b=it is!
diff --git a/doc/faq.html b/doc/faq.html
index 719d1397e..01ef07209 100644
--- a/doc/faq.html
+++ b/doc/faq.html
@@ -195,6 +195,7 @@ Miller commands were run with pretty-print-tabular output format.
 &bull;&nbsp;<a href="#How_do_I_examine_then-chaining?">How do I examine then-chaining?</a><br/>
 &bull;&nbsp;<a href="#I_assigned_$9_and_it&rsquo;s_not_9th">I assigned $9 and it&rsquo;s not 9th</a><br/>
 &bull;&nbsp;<a href="#How_can_I_handle_field_names_with_special_symbols_in_them?">How can I handle field names with special symbols in them?</a><br/>
+&bull;&nbsp;<a href="#How_to_escape_'?'_in_regexes?">How to escape '?' in regexes?</a><br/>
 &bull;&nbsp;<a href="#How_can_I_put_single-quotes_into_strings?">How can I put single-quotes into strings?</a><br/>
 &bull;&nbsp;<a href="#Why_doesn&rsquo;t_mlr_cut_put_fields_in_the_order_I_want?">Why doesn&rsquo;t mlr cut put fields in the order I want?</a><br/>
 &bull;&nbsp;<a href="#NR_is_not_consecutive_after_then-chaining">NR is not consecutive after then-chaining</a><br/>
@@ -596,6 +597,45 @@ x.a=3,y:b=4,z/c=5,product.all=60
 </div>
 <p/>
 
+</div>
+<a id="How_to_escape_'?'_in_regexes?"/><h1>How to escape '?' in regexes?</h1>
+<button style="font-weight:bold;color:maroon;border:0" padding=0 onclick="toggle_by_name('section_toggle_escape_in_regex');" href="javascript:;">Toggle section visibility</button>
+<div id="section_toggle_escape_in_regex" style="display: block">
+
+<p/> One way is to use square brackets; an alternative is to use simple
+string-substitution rather than a regular expression.
+
+<p/>
+<div class="pokipanel">
+<pre>
+$ cat data/question.dat
+a=is it?,b=it is!
+</pre>
+</div>
+<p/>
+<p/>
+<div class="pokipanel">
+<pre>
+$ mlr --oxtab put '$c = gsub($a, "[?]"," ...")' data/question.dat
+a is it?
+b it is!
+c is it ...
+</pre>
+</div>
+<p/>
+<p/>
+<div class="pokipanel">
+<pre>
+$ mlr --oxtab put '$c = ssub($a, "?"," ...")' data/question.dat
+a is it?
+b it is!
+c is it ...
+</pre>
+</div>
+<p/>
+
+<p/> The <tt>ssub</tt> function exists precisely for this reason: so you don&rsquo;t have to escape anything.
+
 </div>
 <a id="How_can_I_put_single-quotes_into_strings?"/><h1>How can I put single-quotes into strings?</h1>
 <button style="font-weight:bold;color:maroon;border:0" padding=0 onclick="toggle_by_name('section_toggle_single_quotes_in_strings');" href="javascript:;">Toggle section visibility</button>