ch47_04.htm

the unix power tools

COLSPAN="1"
><P
CLASS="para"
>Bitwise AND.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>^</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>Bitwise exclusive OR.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>|</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>Bitwise OR.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>&amp;&amp;</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>Logical AND.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>||</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>Logical OR.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>{ <CODE
CLASS="replaceable"
><I
>cmd</I
></CODE
> }</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>Return 1 if command <EM
CLASS="emphasis"
>cmd</EM
> is successful; 0 otherwise.
Note that this is the opposite of <EM
CLASS="emphasis"
>cmd</EM
>'s normal return code.
The <EM
CLASS="emphasis"
>status</EM
> variable may be more practical.</P
></TD
></TR
></TBODY
></TABLE
></P
></DIV
><DIV
CLASS="sect3"
><H4
CLASS="sect3"
><A
CLASS="title"
NAME="UPT-ART-7650-SECT-1.3.4"
>47.4.3.4 Comparison Operators </A
></H4
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-57067"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57070"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57073"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57076"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57079"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57082"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57085"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57088"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57091"
></A
>

<TABLE
CLASS="informaltable"
><TBODY
CLASS="tbody"
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>==  !=</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>Equality; inequality.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>&lt;=  &gt;=</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>Less than or equal to; greater than or equal to.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>&lt;  &gt;</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>Less than; greater than.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>=~</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>String on left matches a filename pattern on the right
containing <CODE
CLASS="literal"
>*</CODE
>, <CODE
CLASS="literal"
>?</CODE
>, or <CODE
CLASS="literal"
>[</CODE
>...<CODE
CLASS="literal"
>]</CODE
>.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>!~</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>String on left does not match a filename pattern
containing <CODE
CLASS="literal"
>*</CODE
>, <CODE
CLASS="literal"
>?</CODE
>, or <CODE
CLASS="literal"
>[</CODE
>...<CODE
CLASS="literal"
>]</CODE
>.</P
></TD
></TR
></TBODY
></TABLE
></P
></DIV
><DIV
CLASS="sect3"
><H4
CLASS="sect3"
><A
CLASS="title"
NAME="UPT-ART-7650-SECT-1.3.5"
>47.4.3.5 File Inquiry Operators </A
></H4
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-57133"
></A
>Command substitution and filename expansion are performed on
<EM
CLASS="emphasis"
>file</EM
> before the test is performed.<A
CLASS="indexterm"
NAME="AUTOID-57137"
></A
>

<TABLE
CLASS="informaltable"
><TBODY
CLASS="tbody"
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>-d <CODE
CLASS="replaceable"
><I
>file</I
></CODE
></P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>The file is a directory.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>-e <CODE
CLASS="replaceable"
><I
>file</I
></CODE
></P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>The file exists.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>-f <CODE
CLASS="replaceable"
><I
>file</I
></CODE
></P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>The file is a plain file.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>-o <CODE
CLASS="replaceable"
><I
>file</I
></CODE
></P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>The user owns the file.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>-r <CODE
CLASS="replaceable"
><I
>file</I
></CODE
></P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>The user has read permission.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>-w <CODE
CLASS="replaceable"
><I
>file</I
></CODE
></P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>The user has write permission.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>-x <CODE
CLASS="replaceable"
><I
>file</I
></CODE
></P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>The user has execute permission.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>-z <CODE
CLASS="replaceable"
><I
>file</I
></CODE
></P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>The file has zero size.</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>!</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>Reverse the sense of any of the above inquiries.</P
></TD
></TR
></TBODY
></TABLE
></P
></DIV
></DIV
><DIV
CLASS="sect2"
><H3
CLASS="sect2"
><A
CLASS="title"
NAME="UPT-ART-7650-SECT-1.4"
>47.4.4 Examples</A
></H3
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-57198"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57200"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57203"
></A
>The following examples show <CODE
CLASS="literal"
>@</CODE
> commands and assume
<EM
CLASS="emphasis"
>n</EM
> = 4:

<TABLE
CLASS="informaltable"
><THEAD
CLASS="thead"
><TR
CLASS="row"
VALIGN="TOP"
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
>Expression</TH
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
>Value of $x</TH
></TR
></THEAD
><TBODY
CLASS="tbody"
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>@ x = ($n &gt; 10 || $n &lt; 5)</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>1</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>@ x = ($n &gt;= 0 &amp;&amp; $n &lt; 3)</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>0</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>@ x = ($n &lt;&lt; 2)</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>16</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>@ x = ($n &gt;&gt; 2)</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>1</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>@ x = $n % 2</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>0</TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>@ x = $n % 3</TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
>1</TD
></TR
></TBODY
></TABLE
></P
><P
CLASS="para"
>The following examples show the first line of <EM
CLASS="emphasis"
>if</EM
> or
<EM
CLASS="emphasis"
>while</EM
> statements:

<TABLE
CLASS="informaltable"
><THEAD
CLASS="thead"
><TR
CLASS="row"
VALIGN="TOP"
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>Expression</P
></TH
><TH
CLASS="entry"
ALIGN="LEFT"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>Meaning</P
></TH
></TR
></THEAD
><TBODY
CLASS="tbody"
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>while ($#argv != 0)</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>While there are command-line (<EM
CLASS="emphasis"
>argv</EM
>) arguments ...</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>if ($today[1] == Fri)</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>If the first word is <EM
CLASS="emphasis"
>Fri</EM
>...</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>if ($file !~ *.[zZ])</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>If the file doesn't end with <EM
CLASS="emphasis"
>.z</EM
> or <EM
CLASS="emphasis"
>.Z</EM
> ...</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>if ($argv[1] =~ chap?)</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>If the first argument is <EM
CLASS="emphasis"
>chap</EM
> followed by a single character...</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>if (-f $argv[1])</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>If the first argument is a plain file...</P
></TD
></TR
><TR
CLASS="row"
VALIGN="TOP"
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>if (! -d $tmpdir)</P
></TD
><TD
CLASS="entry"
ROWSPAN="1"
COLSPAN="1"
><P
CLASS="para"
>If <EM
CLASS="emphasis"
>tmpdir</EM
> is not a directory...</P
></TD
></TR
></TBODY
></TABLE
><A
CLASS="indexterm"
NAME="AUTOID-57281"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57284"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57287"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57290"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57293"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57296"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57299"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57302"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57305"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57308"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57311"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57314"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57317"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57320"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57323"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57326"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57329"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57332"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57335"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57338"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57341"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57344"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57347"
></A
><A
CLASS="indexterm"
NAME="AUTOID-57350"
></A
></P
></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
></DIV
></DIV
><DIV
CLASS="htmlnav"
><P
></P
><HR
ALIGN="LEFT"
WIDTH="515"
TITLE="footer"><TABLE
WIDTH="515"
BORDER="0"
CELLSPACING="0"
CELLPADDING="0"
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="172"
><A
CLASS="SECT1"
HREF="ch47_03.htm"
TITLE="47.3 Conditional Statements with if "
><IMG
SRC="gifs/txtpreva.gif"
SRC="gifs/txtpreva.gif"
ALT="Previous: 47.3 Conditional Statements with if "
BORDER="0"></A
></TD
><TD
ALIGN="CENTER"
VALIGN="TOP"
WIDTH="171"
><A
CLASS="book"
HREF="index.htm"
TITLE="UNIX Power Tools"
><IMG
SRC="gifs/txthome.gif"
SRC="gifs/txthome.gif"
ALT="UNIX Power Tools"
BORDER="0"></A
></TD
><TD
ALIGN="RIGHT"
VALIGN="TOP"
WIDTH="172"
><A
CLASS="SECT1"
HREF="ch47_05.htm"
TITLE="47.5 Using C Shell Arrays "
><IMG
SRC="gifs/txtnexta.gif"
SRC="gifs/txtnexta.gif"
ALT="Next: 47.5 Using C Shell Arrays "
BORDER="0"></A
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="172"
>47.3 Conditional Statements with if </TD
><TD
ALIGN="CENTER"
VALIGN="TOP"
WIDTH="171"
><A
CLASS="index"
HREF="index/idx_0.htm"
TITLE="Book Index"
><IMG
SRC="gifs/index.gif"
SRC="gifs/index.gif"
ALT="Book Index"
BORDER="0"></A
></TD
><TD
ALIGN="RIGHT"
VALIGN="TOP"
WIDTH="172"
>47.5 Using C Shell Arrays </TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="515"
TITLE="footer"><IMG
SRC="gifs/smnavbar.gif"
SRC="gifs/smnavbar.gif"
USEMAP="#map"
BORDER="0"
ALT="The UNIX CD Bookshelf Navigation"><MAP
NAME="map"
><AREA
SHAPE="RECT"
COORDS="0,0,73,21"
HREF="../index.htm"
ALT="The UNIX CD Bookshelf"><AREA
SHAPE="RECT"
COORDS="74,0,163,21"
HREF="index.htm"
ALT="UNIX Power Tools"><AREA
SHAPE="RECT"
COORDS="164,0,257,21"
HREF="../unixnut/index.htm"
ALT="UNIX in a Nutshell"><AREA
SHAPE="RECT"
COORDS="258,0,321,21"
HREF="../vi/index.htm"
ALT="Learning the vi Editor"><AREA
SHAPE="RECT"
COORDS="322,0,378,21"
HREF="../sedawk/index.htm"
ALT="sed &amp; awk"><AREA
SHAPE="RECT"
COORDS="379,0,438,21"
HREF="../ksh/index.htm"
ALT="Learning the Korn Shell"><AREA
SHAPE="RECT"
COORDS="439,0,514,21"
HREF="../lrnunix/index.htm"
ALT="Learning the UNIX Operating System"></MAP
></DIV
></BODY
></HTML
>