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Regex
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<b>6.</b>
$0=$0, $1=$1
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<b>8.</b>
getline
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<b>9.</b>
Arrays
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<b>9.1.</b>
Sort
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<b>9.2.</b>
GROUP BY
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<b>9.3.</b>
JOIN
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<b>9.4.</b>
Subquery
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<b>9.5.</b>
Index
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<b>10.</b>
Control Statements
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<b>11.</b>
Operators
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<b>12.</b>
Built-in Functions
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<b>12.1.</b>
Numeric Functions
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<b>12.2.</b>
String Functions
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<b>12.3.</b>
I/O Functions
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<b>12.4.</b>
Time Functions
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<b>12.5.</b>
Bitwise Functions
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<b>12.6.</b>
Type Functions
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Dynamic Extensions
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<b>13.1.</b>
예제
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<b>14.</b>
TCP/IP Internetworking
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<b>15.</b>
Command-line options
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Debugging
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Tips
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<section class="normal" id="section-">
<h1 id="control-statements">Control Statements</h1>
<p>awk 에 특화된 <code>next</code>, <code>nextfile</code> 구문을 제외하고 나머지는 프로그래밍 언어와 사용 방법이 같습니다.</p>
<h3 id="next">next</h3>
<p>현재 처리 중인 레코드를 중단하고 다음 레코드로 이동합니다.</p>
<h3 id="nextfile">nextfile</h3>
<p>현재 처리 중인 파일을 중단하고 다음 파일로 이동합니다.</p>
<h3 id="ifelse">if-else</h3>
<p><img src="images/control_statements/if-else.png" alt=""></p>
<pre><code class="lang-bash"><span class="hljs-keyword">if</span> (x % <span class="hljs-number">2</span> == <span class="hljs-number">0</span>) <span class="hljs-keyword">if</span> ( x == <span class="hljs-number">1</span> )
<span class="hljs-built_in">print</span> <span class="hljs-string">"x is even"</span> <span class="hljs-built_in">print</span> <span class="hljs-string">"x is 1"</span>
<span class="hljs-keyword">else</span> <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> ( y == <span class="hljs-number">2</span> )
<span class="hljs-built_in">print</span> <span class="hljs-string">"x is odd"</span> <span class="hljs-built_in">print</span> <span class="hljs-string">"y is 2"</span>
<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> ( z == <span class="hljs-number">3</span> )
<span class="hljs-built_in">print</span> <span class="hljs-string">"z is 3"</span>
<span class="hljs-keyword">else</span>
<span class="hljs-built_in">print</span> <span class="hljs-string">"default"</span>
</code></pre>
<h3 id="while">while</h3>
<p><img src="images/control_statements/while.png" alt=""></p>
<pre><code class="lang-bash">num = <span class="hljs-number">1</span>
<span class="hljs-keyword">while</span> ( num <= <span class="hljs-number">10</span> ) {
<span class="hljs-built_in">print</span> num
num++
}
</code></pre>
<h3 id="dowhile">do-while</h3>
<p><img src="images/control_statements/do-while.png" alt=""></p>
<pre><code class="lang-bash">num = <span class="hljs-number">1</span>
<span class="hljs-keyword">do</span> {
<span class="hljs-built_in">print</span> num
num++
} <span class="hljs-keyword">while</span> ( num <= <span class="hljs-number">10</span> )
</code></pre>
<h3 id="for">for</h3>
<p><img src="images/control_statements/for.png" alt=""></p>
<pre><code class="lang-bash"><span class="hljs-keyword">for</span> (i = <span class="hljs-number">1</span>; i <= <span class="hljs-number">10</span>; i++)
<span class="hljs-built_in">print</span> i
........................
<span class="hljs-comment"># array 원소 추출</span>
<span class="hljs-keyword">for</span> (idx <span class="hljs-keyword">in</span> arr) {
<span class="hljs-built_in">printf</span> <span class="hljs-string">"index: %s, value: %s\n"</span> ,idx ,arr[idx]
}
</code></pre>
<h3 id="switch">switch</h3>
<p>case 문에 regex 을 사용할 수 있는데 이때는 regex 상수를 사용합니다.</p>
<p><img src="images/control_statements/switch.png" alt=""></p>
<pre><code class="lang-bash">$ awk <span class="hljs-string">'{ $ echo -e "a\nb\nc\nd" | awk '</span>{
switch (<span class="hljs-variable">$2</span>) { switch(<span class="hljs-variable">$0</span>) {
<span class="hljs-keyword">case</span> <span class="hljs-string">"+"</span> : <span class="hljs-keyword">case</span> <span class="hljs-string">"a"</span> :
res = <span class="hljs-variable">$1</span> + <span class="hljs-variable">$3</span> <span class="hljs-keyword">case</span> <span class="hljs-string">"b"</span> :
<span class="hljs-built_in">break</span> <span class="hljs-built_in">print</span> <span class="hljs-number">111</span>
<span class="hljs-keyword">case</span> <span class="hljs-string">"-"</span> : <span class="hljs-built_in">break</span>
res = <span class="hljs-variable">$1</span> - <span class="hljs-variable">$3</span> <span class="hljs-keyword">case</span> <span class="hljs-string">"c"</span> :
<span class="hljs-built_in">break</span> <span class="hljs-keyword">case</span> <span class="hljs-string">"d"</span> :
<span class="hljs-keyword">case</span> <span class="hljs-string">"*"</span> : <span class="hljs-built_in">print</span> <span class="hljs-number">222</span>
res = <span class="hljs-variable">$1</span> * <span class="hljs-variable">$3</span> }
<span class="hljs-built_in">break</span> }<span class="hljs-string">'
case "/" :
res = $1 / $3 ####### 실행 결과 ######
break 111
default : 111
print "Error" 222
next 222
}
print res
}'</span>
<span class="hljs-comment">####### 실행 결과 #######</span>
<span class="hljs-number">1</span> + <span class="hljs-number">2</span>
<span class="hljs-number">3</span>
<span class="hljs-number">2</span> * <span class="hljs-number">3</span>
<span class="hljs-number">6</span>
<span class="hljs-number">5</span> -<span class="hljs-number">2</span>
Error
<span class="hljs-number">5</span> - <span class="hljs-number">2</span>
<span class="hljs-number">3</span>
<span class="hljs-number">12</span> / <span class="hljs-number">3</span>
<span class="hljs-number">4</span>
</code></pre>
<h3 id="break">break</h3>
<p>while, do-while, for, switch 문에서 사용되는 것으로 반복문 실행을 중단합니다.<br>반복문이 중첩되어 실행되는 경우는 break 문이 위치한 안쪽 블록만 중단됩니다.</p>
<h3 id="continue">continue</h3>
<p>while, do-while, for 문에서 사용되는 것으로 뒤에 이어지는 실행문을 skip 하고 다음 반복을 시작합니다.</p>
<h3 id="exit">exit</h3>
<p>awk 실행을 중지하고 exit 합니다.</p>
<h1 id="quiz">Quiz</h1>
<p>JSON 데이터를 파싱 해서 pretty printing 하는 것입니다.
데이터를 기본 단위인 token 으로 분리해놓아야
shell 의 <a href="https://mug896.github.io/bash-shell/command_completion.html" target="_blank">command completion</a>
에서처럼 앞, 뒤 token 을 참조하면서 컨트롤하기 좋습니다.</p>
<p><img src="images/number_regex.gif" alt=""></p>
<p><a href="https://www.json.org" target="_blank">https://www.json.org</a></p>
<pre><code class="lang-bash">$ cat json.sh
<span class="hljs-comment">#!/usr/bin/env -S gawk -f</span>
BEGIN {
RS=<span class="hljs-string">"(.)"</span> <span class="hljs-comment"># 한 문자씩 읽어 들입니다. (getline 도 마찬가지)</span>
<span class="hljs-keyword">if</span> (!INDENT) INDENT = <span class="hljs-number">2</span>; <span class="hljs-comment"># 기본 indent 크기</span>
keyword[<span class="hljs-string">"true"</span>]; keyword[<span class="hljs-string">"false"</span>]; keyword[<span class="hljs-string">"null"</span>] <span class="hljs-comment"># json 키워드</span>
token[<span class="hljs-number">0</span>]; idx = <span class="hljs-number">0</span> <span class="hljs-comment"># idx 변수는 token 배열의 index 로 사용</span>
}
{ tokenize(RT) }
END {
pretty_<span class="hljs-built_in">print</span>()
}
<span class="hljs-comment"># { } [ ] : , 는 json 에서 사용되는 문자</span>
<span class="hljs-keyword">function</span> tokenize (char) {
switch (char) {
<span class="hljs-keyword">case</span> <span class="hljs-string">"{"</span> : <span class="hljs-keyword">case</span> <span class="hljs-string">"}"</span> :
<span class="hljs-keyword">case</span> <span class="hljs-string">"["</span> : <span class="hljs-keyword">case</span> <span class="hljs-string">"]"</span> :
<span class="hljs-keyword">case</span> <span class="hljs-string">":"</span> : <span class="hljs-keyword">case</span> <span class="hljs-string">","</span> : token[idx++] = char; <span class="hljs-built_in">break</span>
<span class="hljs-keyword">case</span> <span class="hljs-string">"\""</span> : t_string(); <span class="hljs-built_in">break</span>
<span class="hljs-keyword">case</span> /[<span class="hljs-number">0</span>-<span class="hljs-number">9</span>-]/ : t_number(char); <span class="hljs-built_in">break</span>
<span class="hljs-keyword">case</span> /[a-z]/ : t_keyword(char); <span class="hljs-built_in">break</span>
}
}
<span class="hljs-keyword">function</span> t_keyword (str) {
<span class="hljs-keyword">while</span> (getline) {
<span class="hljs-keyword">if</span> ( RT ~ /[a-z]/ ) str = str RT
<span class="hljs-keyword">else</span> {
<span class="hljs-keyword">if</span> ( str <span class="hljs-keyword">in</span> keyword ) token[idx++] = str
<span class="hljs-built_in">break</span>
}
}
tokenize(RT)
}
<span class="hljs-keyword">function</span> t_number (str) {
<span class="hljs-keyword">while</span> (getline) {
<span class="hljs-keyword">if</span> ( RT ~ /[<span class="hljs-number">0</span>-<span class="hljs-number">9</span>.eE+-]/ ) str = str RT
<span class="hljs-keyword">else</span> {
<span class="hljs-keyword">if</span> ( str ~ /^-?(<span class="hljs-number">0</span>|[<span class="hljs-number">1</span>-<span class="hljs-number">9</span>][<span class="hljs-number">0</span>-<span class="hljs-number">9</span>]*)(\.[<span class="hljs-number">0</span>-<span class="hljs-number">9</span>]+)?([eE][+-]?[<span class="hljs-number">0</span>-<span class="hljs-number">9</span>]+)?$/ )
token[idx++] = str
<span class="hljs-built_in">break</span>
}
}
tokenize(RT)
}
<span class="hljs-keyword">function</span> t_string ( str, prev) {
<span class="hljs-keyword">while</span> (getline) {
<span class="hljs-keyword">if</span> ( RT != <span class="hljs-string">"\""</span> ) str = str RT
<span class="hljs-keyword">else</span> {
<span class="hljs-keyword">if</span> ( prev == <span class="hljs-string">"\\"</span> ) str = str RT
<span class="hljs-keyword">else</span> {
token[idx++] = <span class="hljs-string">"\""</span> str <span class="hljs-string">"\""</span>
<span class="hljs-built_in">break</span>
}
}
prev = RT
}
}
<span class="hljs-keyword">function</span> space (depth, i, sp) {
depth = depth * INDENT
<span class="hljs-keyword">for</span> (i=<span class="hljs-number">0</span>; i < depth; i++) sp = sp <span class="hljs-string">" "</span>
<span class="hljs-built_in">return</span> sp
}
<span class="hljs-keyword">function</span> pretty_<span class="hljs-built_in">print</span> ( i, depth, prev, cur) {
<span class="hljs-keyword">for</span> (i <span class="hljs-keyword">in</span> token) {
prev = cur; cur = token[i]
switch (cur) {
<span class="hljs-keyword">case</span> <span class="hljs-string">"{"</span> :
<span class="hljs-built_in">printf</span> (prev == <span class="hljs-string">":"</span> ? <span class="hljs-string">""</span> : <span class="hljs-string">"\n"</span> space(depth)) <span class="hljs-string">"{"</span>
depth++; <span class="hljs-built_in">break</span>
<span class="hljs-keyword">case</span> <span class="hljs-string">"}"</span> :
depth--
<span class="hljs-built_in">printf</span> (prev == <span class="hljs-string">"{"</span> ? <span class="hljs-string">" "</span> : <span class="hljs-string">"\n"</span> space(depth)) <span class="hljs-string">"}"</span>
<span class="hljs-built_in">break</span>
<span class="hljs-keyword">case</span> <span class="hljs-string">"["</span> :
<span class="hljs-built_in">printf</span> (prev == <span class="hljs-string">":"</span> ? <span class="hljs-string">""</span> : <span class="hljs-string">"\n"</span> space(depth)) <span class="hljs-string">"["</span>
depth++; <span class="hljs-built_in">break</span>
<span class="hljs-keyword">case</span> <span class="hljs-string">"]"</span> :
depth--
<span class="hljs-built_in">printf</span> (prev == <span class="hljs-string">"["</span> ? <span class="hljs-string">" "</span> : <span class="hljs-string">"\n"</span> space(depth)) <span class="hljs-string">"]"</span>
<span class="hljs-built_in">break</span>
<span class="hljs-keyword">case</span> <span class="hljs-string">","</span> : <span class="hljs-built_in">printf</span> <span class="hljs-string">","</span>; <span class="hljs-built_in">break</span>
<span class="hljs-keyword">case</span> <span class="hljs-string">":"</span> : <span class="hljs-built_in">printf</span> <span class="hljs-string">": "</span>; <span class="hljs-built_in">break</span>
default :
<span class="hljs-comment"># "%" 문자는 printf 문에서 format specifier 를 작성할 때 사용되므로</span>
<span class="hljs-comment"># "%" 문자가 그대로 출력되려면 "%%" 로 변경해야 합니다.</span>
<span class="hljs-built_in">printf</span> (prev == <span class="hljs-string">":"</span> ? <span class="hljs-string">""</span> : <span class="hljs-string">"\n"</span> space(depth)) gensub(/%/,<span class="hljs-string">"%%"</span>,<span class="hljs-string">"g"</span>,cur)
}
<span class="hljs-keyword">if</span> (depth == <span class="hljs-number">0</span>) <span class="hljs-built_in">break</span>
}
<span class="hljs-built_in">print</span> <span class="hljs-string">""</span>
}
</code></pre>
<pre><code class="lang-bash">$ cat sample.json
{<span class="hljs-string">"squadName"</span>:<span class="hljs-string">"Super hero squad"</span>,<span class="hljs-string">"homeTown"</span>:<span class="hljs-string">"Metro City"</span>,<span class="hljs-string">"formed"</span>:<span class="hljs-number">2016</span>,<span class="hljs-string">"secretBase"</span>:
<span class="hljs-string">"Super tower"</span>,<span class="hljs-string">"active"</span>:<span class="hljs-literal">true</span>,<span class="hljs-string">"members"</span>:[{<span class="hljs-string">"name"</span>:<span class="hljs-string">"Molecule Man"</span>,<span class="hljs-string">"age"</span>:<span class="hljs-number">29</span>,<span class="hljs-string">"secretIdentity"</span>:
<span class="hljs-string">"Dan Jukes"</span>,<span class="hljs-string">"powers"</span>:[<span class="hljs-string">"Radiation resistance"</span>,<span class="hljs-string">"Turning tiny"</span>,<span class="hljs-string">"Radiation blast"</span>]},{<span class="hljs-string">"name"</span>:
<span class="hljs-string">"Madame Uppercut"</span>,<span class="hljs-string">"age"</span>:<span class="hljs-number">39</span>,<span class="hljs-string">"secretIdentity"</span>:<span class="hljs-string">"Jane Wilson"</span>,<span class="hljs-string">"powers"</span>:[<span class="hljs-string">"Million tonne punch"</span>,
<span class="hljs-string">"Damage resistance"</span>,<span class="hljs-string">"Superhuman reflexes"</span>]},{<span class="hljs-string">"name"</span>:<span class="hljs-string">"Eternal Flame"</span>,<span class="hljs-string">"age"</span>:<span class="hljs-number">1000000</span>,
<span class="hljs-string">"secretIdentity"</span>:<span class="hljs-string">"Unknown"</span>,<span class="hljs-string">"powers"</span>:[<span class="hljs-string">"Immortality"</span>,<span class="hljs-string">"Heat Immunity"</span>,<span class="hljs-string">"Teleportation"</span>,
<span class="hljs-string">"Interdimensional travel"</span>]}]}
$ ./json.sh sample.json
{
<span class="hljs-string">"squadName"</span>: <span class="hljs-string">"Super hero squad"</span>,
<span class="hljs-string">"homeTown"</span>: <span class="hljs-string">"Metro City"</span>,
<span class="hljs-string">"formed"</span>: <span class="hljs-number">2016</span>,
<span class="hljs-string">"secretBase"</span>: <span class="hljs-string">"Super tower"</span>,
<span class="hljs-string">"active"</span>: <span class="hljs-literal">true</span>,
<span class="hljs-string">"members"</span>: [
{
<span class="hljs-string">"name"</span>: <span class="hljs-string">"Molecule Man"</span>,
<span class="hljs-string">"age"</span>: <span class="hljs-number">29</span>,
<span class="hljs-string">"secretIdentity"</span>: <span class="hljs-string">"Dan Jukes"</span>,
<span class="hljs-string">"powers"</span>: [
<span class="hljs-string">"Radiation resistance"</span>,
<span class="hljs-string">"Turning tiny"</span>,
<span class="hljs-string">"Radiation blast"</span>
]
},
{
<span class="hljs-string">"name"</span>: <span class="hljs-string">"Madame Uppercut"</span>,
<span class="hljs-string">"age"</span>: <span class="hljs-number">39</span>,
<span class="hljs-string">"secretIdentity"</span>: <span class="hljs-string">"Jane Wilson"</span>,
<span class="hljs-string">"powers"</span>: [
<span class="hljs-string">"Million tonne punch"</span>,
<span class="hljs-string">"Damage resistance"</span>,
<span class="hljs-string">"Superhuman reflexes"</span>
]
},
{
<span class="hljs-string">"name"</span>: <span class="hljs-string">"Eternal Flame"</span>,
<span class="hljs-string">"age"</span>: <span class="hljs-number">1000000</span>,
<span class="hljs-string">"secretIdentity"</span>: <span class="hljs-string">"Unknown"</span>,
<span class="hljs-string">"powers"</span>: [
<span class="hljs-string">"Immortality"</span>,
<span class="hljs-string">"Heat Immunity"</span>,
<span class="hljs-string">"Teleportation"</span>,
<span class="hljs-string">"Interdimensional travel"</span>
]
}
]
}
</code></pre>
<blockquote>
<p><code>RT</code> 변수를 사용하지 않고 처리하는 방법은 <a href="https://github.com/mug896/awk-json/blob/master/json.sh" target="_blank">여기</a> 를 참조하세요.</p>
</blockquote>
<h1 id="2-">2 .</h1>
<p>이번에는 검색 기능을 추가하는 것입니다.
사용할 수 있는 옵션은 <code>-k</code> , <code>-s</code> 두 가지가 있는데
<code>-k</code> 옵션은 전체 데이터에서 key 만 뽑아서 계층 구조로 출력합니다.
구분자는 디렉토리 경로와 같이 <code>/</code> 문자로 하였습니다.
<code>-s</code> 옵션은 검색할 때 사용하는데 앞서 출력된 key 값들 중 하나를 설정하면
해당 key 와 매칭되는 value 들을 출력합니다.
<code>key=value</code> 형태로 검색할 수도 있는데 이때는 매칭되는 값이 존재하는
블록 전체를 표시합니다.</p>
<pre><code class="lang-bash">$ ./json.sh -k sample.json <span class="hljs-comment"># 전체 key 값을 출력</span>
/squadName
/homeTown
/formed
/secretBase
/active
/members
/members/name
/members/age
/members/secretIdentity
/members/powers
/members/name
/members/age
/members/secretIdentity
/members/powers
/members/name
/members/age
/members/secretIdentity
/members/powers
<span class="hljs-comment"># key 값이 /members/name 인 value 를 모두 출력</span>
$ ./json.sh <span class="hljs-operator">-s</span> /members/name sample.json
<span class="hljs-string">"Molecule Man"</span>
<span class="hljs-string">"Madame Uppercut"</span>
<span class="hljs-string">"Eternal Flame"</span>
<span class="hljs-comment"># /members/name 의 value 가 "Molecule Man" 인 블록을 출력</span>
$ ./json.sh <span class="hljs-operator">-s</span> /members/name=<span class="hljs-string">"Molecule Man"</span> sample.json
{
<span class="hljs-string">"name"</span>: <span class="hljs-string">"Molecule Man"</span>,
<span class="hljs-string">"age"</span>: <span class="hljs-number">29</span>,
<span class="hljs-string">"secretIdentity"</span>: <span class="hljs-string">"Dan Jukes"</span>,
<span class="hljs-string">"powers"</span>: [
<span class="hljs-string">"Radiation resistance"</span>,
<span class="hljs-string">"Turning tiny"</span>,
<span class="hljs-string">"Radiation blast"</span>
]
}
<span class="hljs-comment"># shell 에서 파이프와 함께 사용할 때는 stdin 을 나타내는 "-" 를 사용하면 됩니다.</span>
$ cat sample.json | ./json.sh <span class="hljs-operator">-s</span> /members/name=<span class="hljs-string">"Molecule Man"</span> -
</code></pre>
<p>코드는 처음 예제와 동일한데 검색 기능을 위해서 search 함수가 추가되고
명령 라인 인수를 처리하기 위해 <code>BEGINFILE</code> 블록이 추가되었습니다.
shebang 라인을 보면 <code>gawk -f</code> 에서 <code>gawk -E</code> 로 변경된 것을 볼 수 있습니다.</p>
<pre><code class="lang-bash"><span class="hljs-comment">#!/usr/bin/env -S gawk -E</span>
BEGIN {
RS=<span class="hljs-string">"(.)"</span>
INDENT = <span class="hljs-number">2</span>;
keyword[<span class="hljs-string">"true"</span>]; keyword[<span class="hljs-string">"false"</span>]; keyword[<span class="hljs-string">"null"</span>]
token[<span class="hljs-number">0</span>] = opt1 = opt2 = <span class="hljs-string">""</span>
idx = cdx = <span class="hljs-number">0</span>
}
BEGINFILE {
<span class="hljs-keyword">if</span> ( FILENAME ~ /^-k$|^<span class="hljs-operator">-s</span>$/ ) { opt1 = FILENAME; nextfile }
<span class="hljs-keyword">if</span> ( opt1 == <span class="hljs-string">"-s"</span> && opt2 == <span class="hljs-string">""</span> ) { opt2 = FILENAME; nextfile }
}
{ tokenize(RT) }
END {
<span class="hljs-keyword">if</span> (opt1) search(); <span class="hljs-keyword">else</span> pretty_<span class="hljs-built_in">print</span>(<span class="hljs-number">0</span>)
}