ch33_11.htm

the unix power tools

><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>NR</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Number of the current record</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>OFMT</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Output format for numbers (default is <CODE
CLASS="literal"
>%.6g</CODE
>)</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>OFS</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Output field separator (default is a blank)</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>ORS</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Output record separator (default is a newline)</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>RS</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Record separator (default is a newline)</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><CODE
CLASS="literal"
>$0</CODE
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Entire input record</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><CODE
CLASS="literal"
>$</CODE
><CODE
CLASS="replaceable"
><I
>n</I
></CODE
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><CODE
CLASS="replaceable"
><I
>n</I
></CODE
>th field in current record;
fields are separated by <EM
CLASS="emphasis"
>FS</EM
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>nawk</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>ARGC</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Number of arguments on command line</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>ARGV</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>An array containing the command-line arguments</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>ENVIRON</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>An associative array of environment variables</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>FNR</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Like <EM
CLASS="emphasis"
>NR</EM
>, but relative to the current file</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>RSTART</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>First position in the string matched by <EM
CLASS="emphasis"
>match</EM
> function</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>RLENGTH</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Length of the string matched by <EM
CLASS="emphasis"
>match</EM
> function</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>SUBSEP</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Separator character for array subscripts (default is <CODE
CLASS="literal"
>\034</CODE
>)</TD
></TR
></TBODY
></TABLE
></P
></DIV
><DIV
CLASS="sect2"
><H3
CLASS="sect2"
><A
CLASS="title"
NAME="UPT-ART-2860-SECT-1.4"
>33.11.4 Operators </A
></H3
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-37411"
></A
><A
CLASS="indexterm"
NAME="AUTOID-37414"
></A
>The table below lists the operators,
in order of increasing precedence, that are available in <EM
CLASS="emphasis"
>awk</EM
>:
<TABLE
CLASS="informaltable"
><THEAD
CLASS="thead"
><TR
CLASS="row"
VALIGN="TOP"
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
>Symbol</TH
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
>Meaning</TH
></TR
></THEAD
><TBODY
CLASS="tbody"
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>= += -= *= /= %= ^=</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Assignment (<CODE
CLASS="literal"
>^=</CODE
> only in <EM
CLASS="emphasis"
>nawk</EM
> and <EM
CLASS="emphasis"
>gawk</EM
>)</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>?:</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>C conditional expression (<EM
CLASS="emphasis"
>nawk</EM
> and <EM
CLASS="emphasis"
>gawk</EM
>)</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>||</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Logical OR</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>&amp;&amp;</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Logical AND</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>~  !~</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Match regular expression and negation</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>&lt; &lt;= &gt; &gt;= != ==</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Relational operators</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>(blank)</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Concatenation</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>+ -</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Addition, subtraction</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>* / %</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Multiplication, division, and modulus</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>+ - !</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Unary plus and minus, and logical negation</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>^</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Exponentiation (<EM
CLASS="emphasis"
>nawk</EM
> and <EM
CLASS="emphasis"
>gawk</EM
>)</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>++ -- </TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Increment and decrement, either prefix or postfix</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>$</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>Field reference</TD
></TR
></TBODY
></TABLE
></P
></DIV
><DIV
CLASS="sect2"
><H3
CLASS="sect2"
><A
CLASS="title"
NAME="UPT-ART-2860-SECT-1.5"
>33.11.5 Variables and Array Assignments </A
></H3
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-37474"
></A
><A
CLASS="indexterm"
NAME="AUTOID-37477"
></A
><A
CLASS="indexterm"
NAME="AUTOID-37480"
></A
>Variables can be assigned a value with an equal sign (<CODE
CLASS="literal"
>=</CODE
>). For example:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>FS = &quot;,&quot;</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>Expressions using the operators <CODE
CLASS="literal"
>+</CODE
>, <CODE
CLASS="literal"
>-</CODE
>, <CODE
CLASS="literal"
>*</CODE
>,
<CODE
CLASS="literal"
>/</CODE
>, and <CODE
CLASS="literal"
>%</CODE
> 
(modulo) can be assigned to variables.</P
><P
CLASS="para"
>Arrays can be created with the <EM
CLASS="emphasis"
>split</EM
> function (see below), 
or they can simply be named in an assignment statement.
Array elements can be subscripted with numbers 
(<CODE
CLASS="replaceable"
><I
>array</I
></CODE
><CODE
CLASS="literal"
>[1]</CODE
>,...<CODE
CLASS="replaceable"
><I
>array</I
></CODE
><CODE
CLASS="literal"
>[</CODE
><CODE
CLASS="replaceable"
><I
>n</I
></CODE
><CODE
CLASS="literal"
>]</CODE
>)
or with names. For example, to count the number of occurrences of a
pattern, you could use the following script:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>/<CODE
CLASS="replaceable"
><I
>pattern</I
></CODE
>/ { <CODE
CLASS="replaceable"
><I
>array</I
></CODE
>[&quot;<CODE
CLASS="replaceable"
><I
>pattern</I
></CODE
>&quot;]++ }
END { print <CODE
CLASS="replaceable"
><I
>array</I
></CODE
>[&quot;<CODE
CLASS="replaceable"
><I
>pattern</I
></CODE
>&quot;] }</PRE
></BLOCKQUOTE
></P
></DIV
><DIV
CLASS="sect2"
><H3
CLASS="sect2"
><A
CLASS="title"
NAME="UPT-ART-2860-SECT-1.6"
>33.11.6 Group Listing of awk Commands </A
></H3
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="UPT-ART-2860-IX-COMMANDS-AWK-UTILITY"
></A
><A
CLASS="indexterm"
NAME="UPT-ART-2860-IX-AWK-UTILITY-COMMANDS-LIST-OF"
></A
><EM
CLASS="emphasis"
>awk</EM
> commands may be classified as follows:
<TABLE
CLASS="informaltable"
><THEAD
CLASS="thead"
><TR
CLASS="row"
VALIGN="TOP"
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
>Arithmetic</TH
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
>String</TH
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
>Control Flow</TH
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
>Input/Output</TH
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
>Functions</TH
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
>Functions</TH
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
>Statements</TH
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
>Processing</TH
></TR
></THEAD
><TBODY
CLASS="tbody"
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>atan2*</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>gsub*</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>break</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>close*</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>cos*</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>index</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>continue</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>delete*</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>exp</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>length</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>do/while*</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>getline*</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>int</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>match*</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>exit</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>next</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>log</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>split</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>for</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>print</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>rand*</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>sub*</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>if</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>printf</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>sin*</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>substr</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>return*</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>sprintf</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>sqrt</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>tolower*</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>while</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>system*</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>srand*</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>toupper*</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
></TD
></TR
></TBODY
></TABLE
>
*Not in original <EM
CLASS="emphasis"
>awk</EM
>&#13;</P
></DIV
><DIV
CLASS="sect2"
><H3
CLASS="sect2"
><A
CLASS="title"
NAME="UPT-ART-2860-SECT-1.7"
>33.11.7 Alphabetical Summary of Commands </A
></H3
><P
CLASS="para"
>The following alphabetical list of statements and functions
includes all that are available in <EM
CLASS="emphasis"
>awk</EM
>, <EM
CLASS="emphasis"
>nawk</EM
>, or <EM
CLASS="emphasis"
>gawk</EM
>.
Unless otherwise mentioned, the statement or function is found
in all versions. New statements and functions introduced
with <EM
CLASS="emphasis"
>nawk</EM
> are also found in <EM
CLASS="emphasis"
>gawk</EM
>.</P
><DL
CLASS="variablelist"
><DT
CLASS="term"
><CODE
CLASS="literal"
>atan2</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>atan2(</CODE
><CODE
CLASS="replaceable"
><I
>y</I
></CODE
><CODE
CLASS="literal"
>,</CODE
><CODE
CLASS="replaceable"
><I
>x</I
></CODE
><CODE
CLASS="literal"
>)</CODE
> 
<A
CLASS="indexterm"
NAME="AUTOID-37596"
></A
>
Returns the arctangent of <CODE
CLASS="replaceable"
><I
>y</I
></CODE
>/<CODE
CLASS="replaceable"
><I
>x</I
></CODE
> in radians. (<EM
CLASS="emphasis"
>nawk</EM
>)&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>break</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
>Exit from a <EM
CLASS="emphasis"
>while</EM
>, <EM
CLASS="emphasis"
>for</EM
>, or <EM
CLASS="emphasis"
>do</EM
> loop.<A
CLASS="indexterm"
NAME="AUTOID-37609"
></A
>&#13;</P
></DD
><DT
CLASS="term"
><CODE