ch33_11.htm

the unix power tools

> (the current input line).
Literal
strings must be quoted.
Fields are
printed in the order they are listed.
If separated by commas (<CODE
CLASS="literal"
>,</CODE
>) in the
argument list, they are separated in the output by the <EM
CLASS="emphasis"
>OFS</EM
> character.
If separated by spaces, they are
concatenated in the output.
<CODE
CLASS="replaceable"
><I
>destination</I
></CODE
> is a UNIX redirection or
pipe expression (e.g., <CODE
CLASS="literal"
>&gt;&nbsp;</CODE
><CODE
CLASS="replaceable"
><I
>file</I
></CODE
>) that redirects the 
default standard output.&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>printf</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="replaceable"
><I
>format </I
></CODE
>[<CODE
CLASS="literal"
>, </CODE
><CODE
CLASS="replaceable"
><I
>expression(s)</I
></CODE
>] [<CODE
CLASS="replaceable"
><I
>destination</I
></CODE
>]

Formatted print statement.<A
CLASS="indexterm"
NAME="AUTOID-37930"
></A
>
Fields or variables can be
formatted according to instructions in the <CODE
CLASS="replaceable"
><I
>format</I
></CODE
> argument.
The number of <CODE
CLASS="replaceable"
><I
>expression</I
></CODE
>s must correspond to the number specified in the
format sections.

<CODE
CLASS="replaceable"
><I
>format</I
></CODE
> follows the conventions of the C-language <EM
CLASS="emphasis"
>printf</EM
>
statement.
Here are a few of the most common formats:&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>%s</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
>A string.</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>%d</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
>A decimal number.</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>%</CODE
><CODE
CLASS="replaceable"
><I
>n</I
></CODE
><CODE
CLASS="literal"
>.</CODE
><CODE
CLASS="replaceable"
><I
>m</I
></CODE
><CODE
CLASS="literal"
>f</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
>A floating-point number, where <CODE
CLASS="replaceable"
><I
>n</I
></CODE
> is the total number of digits
and <CODE
CLASS="replaceable"
><I
>m</I
></CODE
> is the number of digits after the decimal point.</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>%</CODE
>[<CODE
CLASS="literal"
>-</CODE
>]<CODE
CLASS="replaceable"
><I
>nc</I
></CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="replaceable"
><I
>n</I
></CODE
> specifies minimum field length for format type <CODE
CLASS="replaceable"
><I
>c</I
></CODE
>, while
<CODE
CLASS="literal"
>-</CODE
> left justifies value in field; otherwise value is right justified.


<CODE
CLASS="replaceable"
><I
>format</I
></CODE
> can also contain embedded escape sequences:
<CODE
CLASS="literal"
>\n</CODE
> (newline) or <CODE
CLASS="literal"
>\t</CODE
>&nbsp;(tab)
are the most common.
<CODE
CLASS="replaceable"
><I
>destination</I
></CODE
> is a UNIX redirection or
pipe expression (e.g., <CODE
CLASS="literal"
>&gt;&nbsp;</CODE
><CODE
CLASS="replaceable"
><I
>file</I
></CODE
>) that redirects the 
default standard output.

Example:

Using the script:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>{printf &quot;The sum on line %s is %d.\n&quot;, NR, $1+$2}</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>The following input line:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>5   5</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>produces this output, followed by a newline:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>The sum on line 1 is 10.</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>rand</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>rand()</CODE
>

Generate a random number between 0 and 1.<A
CLASS="indexterm"
NAME="AUTOID-37988"
></A
>
This function returns the
same series of numbers each time the script is executed, unless the random
number generator is seeded using the <EM
CLASS="emphasis"
>srand(&nbsp;)</EM
> function. (<EM
CLASS="emphasis"
>nawk</EM
>)&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>return</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>return </CODE
>[<CODE
CLASS="replaceable"
><I
>expr</I
></CODE
>]

Used at end of user-defined functions to exit the function,<A
CLASS="indexterm"
NAME="AUTOID-37999"
></A
>
returning value of expression <CODE
CLASS="replaceable"
><I
>expr</I
></CODE
>, if any. (<EM
CLASS="emphasis"
>nawk</EM
>)&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>sin</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>sin(</CODE
><CODE
CLASS="replaceable"
><I
>x</I
></CODE
><CODE
CLASS="literal"
>)</CODE
>
<A
CLASS="indexterm"
NAME="AUTOID-38011"
></A
>
Return sine of <CODE
CLASS="replaceable"
><I
>x</I
></CODE
> (in radians).
(<EM
CLASS="emphasis"
>nawk</EM
>)&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>split</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>split(</CODE
><CODE
CLASS="replaceable"
><I
>string</I
></CODE
><CODE
CLASS="literal"
>,</CODE
><CODE
CLASS="replaceable"
><I
>array</I
></CODE
>[<CODE
CLASS="literal"
>,</CODE
><CODE
CLASS="replaceable"
><I
>sep</I
></CODE
>]<CODE
CLASS="literal"
>)</CODE
>

Split <CODE
CLASS="replaceable"
><I
>string</I
></CODE
> into elements of <CODE
CLASS="replaceable"
><I
>array</I
></CODE
><A
CLASS="indexterm"
NAME="AUTOID-38029"
></A
>
<CODE
CLASS="literal"
>array[1],...

array[</CODE
><CODE
CLASS="replaceable"
><I
>n</I
></CODE
><CODE
CLASS="literal"
>]</CODE
>.
<CODE
CLASS="replaceable"
><I
>string</I
></CODE
>
is split at each occurrence of separator <CODE
CLASS="replaceable"
><I
>sep</I
></CODE
>.
(In <EM
CLASS="emphasis"
>nawk</EM
>, the separator may be a regular expression.)
If <CODE
CLASS="replaceable"
><I
>sep</I
></CODE
> is
not specified, <EM
CLASS="emphasis"
>FS</EM
> is used.
The number of array elements created is
returned.&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>sprintf</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>sprintf (</CODE
><CODE
CLASS="replaceable"
><I
>format </I
></CODE
>[<CODE
CLASS="literal"
>, </CODE
><CODE
CLASS="replaceable"
><I
>expression(s)</I
></CODE
>]<CODE
CLASS="literal"
>)</CODE
>

Return the value of <CODE
CLASS="replaceable"
><I
>expression(s)</I
></CODE
>, using the specified <CODE
CLASS="replaceable"
><I
>format</I
></CODE
><A
CLASS="indexterm"
NAME="AUTOID-38051"
></A
>
(see <EM
CLASS="emphasis"
>printf</EM
>).
Data is formatted but not printed.&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>sqrt</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>sqrt(</CODE
><CODE
CLASS="replaceable"
><I
>arg</I
></CODE
><CODE
CLASS="literal"
>)</CODE
>

Return square root of <CODE
CLASS="replaceable"
><I
>arg</I
></CODE
>.<A
CLASS="indexterm"
NAME="AUTOID-38063"
></A
>&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>srand</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>srand(</CODE
><CODE
CLASS="replaceable"
><I
>expr</I
></CODE
><CODE
CLASS="literal"
>)</CODE
>
<A
CLASS="indexterm"
NAME="AUTOID-38073"
></A
>
Use <CODE
CLASS="replaceable"
><I
>expr</I
></CODE
> to set a new seed for random number generator.
Default is time of day.
Returns the old seed.
(<EM
CLASS="emphasis"
>nawk</EM
>)&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>sub</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>sub(</CODE
><CODE
CLASS="replaceable"
><I
>r</I
></CODE
><CODE
CLASS="literal"
>,</CODE
><CODE
CLASS="replaceable"
><I
>s</I
></CODE
>[<CODE
CLASS="literal"
>,</CODE
><CODE
CLASS="replaceable"
><I
>t</I
></CODE
>]<CODE
CLASS="literal"
>)</CODE
>

Substitute <CODE
CLASS="replaceable"
><I
>s</I
></CODE
> for first match of the<A
CLASS="indexterm"
NAME="AUTOID-38090"
></A
>
regular expression <CODE
CLASS="replaceable"
><I
>r</I
></CODE
> in the string <CODE
CLASS="replaceable"
><I
>t</I
></CODE
>.
Return
1 if successful; 0 otherwise.
If <CODE
CLASS="replaceable"
><I
>t</I
></CODE
> is not supplied,
defaults to <CODE
CLASS="literal"
>$0</CODE
>. (<EM
CLASS="emphasis"
>nawk</EM
>)&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>substr</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>substr(</CODE
><CODE
CLASS="replaceable"
><I
>string</I
></CODE
><CODE
CLASS="literal"
>,</CODE
><CODE
CLASS="replaceable"
><I
>m</I
></CODE
>[<CODE
CLASS="literal"
>,</CODE
><CODE
CLASS="replaceable"
><I
>n</I
></CODE
>]<CODE
CLASS="literal"
>)</CODE
>

Return substring of <CODE
CLASS="replaceable"
><I
>string</I
></CODE
> beginning at character position<A
CLASS="indexterm"
NAME="AUTOID-38110"
></A
>
<CODE
CLASS="replaceable"
><I
>m</I
></CODE
> and consisting of the next <CODE
CLASS="replaceable"
><I
>n</I
></CODE
> characters.
If <CODE
CLASS="replaceable"
><I
>n</I
></CODE
> is
omitted, include all characters to the end of string.&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>system</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>system(</CODE
><CODE
CLASS="replaceable"
><I
>command</I
></CODE
><CODE
CLASS="literal"
>)</CODE
>

Function that executes the specified UNIX <CODE
CLASS="replaceable"
><I
>command</I
></CODE
> and returns its<A
CLASS="indexterm"
NAME="AUTOID-38124"
></A
>
<SPAN
CLASS="link"
>status (<A
CLASS="linkend"
HREF="ch44_07.htm"
TITLE="Exit Status of UNIX Processes "
>44.7</A
>)</SPAN
>.
The status of the command that is executed typically
indicates its success (0) or failure (non-zero).
The output of the command is not available for processing
within the <EM
CLASS="emphasis"
>nawk</EM
> script.
Use <CODE
CLASS="replaceable"
><I
>command</I
></CODE
>&nbsp;<CODE
CLASS="literal"
>|</CODE
>&nbsp;<CODE
CLASS="literal"
>getline</CODE
> to
read the output of the command into the script. (<EM
CLASS="emphasis"
>nawk</EM
>)
&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>tolower</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>tolower(</CODE
><CODE
CLASS="replaceable"
><I
>str</I
></CODE
><CODE
CLASS="literal"
>)</CODE
>

Translate all uppercase characters<A
CLASS="indexterm"
NAME="AUTOID-38140"
></A
>
in <CODE
CLASS="replaceable"
><I
>str</I
></CODE
> to lowercase and return the new string. (<EM
CLASS="emphasis"
>nawk</EM
>)&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>toupper</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><CODE
CLASS="literal"
>toupper(</CODE
><CODE
CLASS="replaceable"
><I
>str</I
></CODE
><CODE
CLASS="literal"
>)</CODE
>

Translate all lowercase characters<A
CLASS="indexterm"
NAME="AUTOID-38152"
></A
>
in <CODE
CLASS="replaceable"
><I
>str</I
></CODE
> to uppercase and return the new string. (<EM
CLASS="emphasis"
>nawk</EM
>)&#13;</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>while</CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
><CODE
CLASS="literal"
>while (</CODE
><CODE
CLASS="replaceable"
><I
>condition</I
></CODE
><CODE
CLASS="literal"
>)</CODE
>
      <CODE
CLASS="replaceable"
><I
>command</I
></CODE
></PRE
></BLOCKQUOTE
>
Do <CODE
CLASS="replaceable"
><I
>command</I
></CODE
> while <CODE
CLASS="replaceable"
><I
>condition</I
></CODE
> is true (see <CODE
CLASS="literal"
>if</CODE
> for a<A
CLASS="indexterm"
NAME="AUTOID-38169"
></A
>
description of allowable conditions).
A series of commands must be put within braces (<CODE
CLASS="literal"
>{}</CODE
>).</P
></DD
></DL
><A
CLASS="indexterm"
NAME="AUTOID-38172"
></A
><A
CLASS="indexterm"
NAME="AUTOID-38173"
></A
><A
CLASS="indexterm"
NAME="AUTOID-38174"
></A
><A
CLASS="indexterm"
NAME="AUTOID-38175"
></A
><A
CLASS="indexterm"
NAME="AUTOID-38176"
></A
></DIV
><DIV
CLASS="sect1info"
><P
CLASS="SECT1INFO"
>- <SPAN
CLASS="authorinitials"
>DG</SPAN
> <SPAN
CLASS="bibliomisc"
>from O'Reilly &amp; Associates' <CITE
CLASS="citetitle"
>UNIX in a Nutshell (SVR4/Solaris)</CITE
></SPAN
></P
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