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<H1> A.15 The Package Command_Line</H1>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> The package Command_Line allows a program to obtain
the values of its arguments and to set the exit status code to be returned
on normal termination. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>1.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Implementation defined: </B>The
meaning of Argument_Count, Argument, and Command_Name.</FONT></DIV>
<H4 ALIGN=CENTER>Static Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> The library package
Ada.Command_Line has the following declaration: </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<DIV Class="Examples"><TT><B>package</B> Ada.Command_Line <B>is</B><A NAME="I6260"></A><A NAME="I6261"></A><A NAME="I6262"></A><BR>
<B>pragma</B> Preelaborate(Command_Line);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<DIV Class="Examples"><TT> <B>function</B> <A NAME="I6263"></A><A NAME="I6264"></A>Argument_Count <B>return</B> Natural;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<DIV Class="Examples"><TT> <B>function</B> <A NAME="I6265"></A><A NAME="I6266"></A>Argument (Number : <B>in</B> Positive) <B>return</B> String;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<DIV Class="Examples"><TT> <B>function</B> <A NAME="I6267"></A><A NAME="I6268"></A>Command_Name <B>return</B> String;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7</FONT></DIV>
<DIV Class="Examples"><TT> <B>type</B> <A NAME="I6269"></A><A NAME="I6270"></A>Exit_Status <B>is</B> <I>implementation-defined integer type</I>;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8</FONT></DIV>
<DIV Class="Examples"><TT> <A NAME="I6271"></A>Success : <B>constant</B> Exit_Status;<BR>
<A NAME="I6272"></A>Failure : <B>constant</B> Exit_Status;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>9</FONT></DIV>
<DIV Class="Examples"><TT> <B>procedure</B> <A NAME="I6273"></A><A NAME="I6274"></A>Set_Exit_Status (Code : <B>in</B> Exit_Status);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>10</FONT></DIV>
<DIV Class="Examples"><TT><B>private</B><BR>
... -- <I>not specified by the language</I><BR>
<B>end</B> Ada.Command_Line;<BR>
</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>11</FONT></DIV>
<DIV Class="Examples"><TT><B>function</B> Argument_Count <B>return</B> Natural;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>12</FONT></DIV>
<DIV Class="CodeIndented" Style="margin-bottom: 0.9em">If the external
execution environment supports passing arguments to a program, then Argument_Count
returns the number of arguments passed to the program invoking the function.
Otherwise it returns 0. The meaning of ``number of arguments'' is implementation
defined.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>13</FONT></DIV>
<DIV Class="Examples"><TT><B>function</B> Argument (Number : <B>in</B> Positive) <B>return</B> String;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>14</FONT></DIV>
<DIV Class="CodeIndented" Style="margin-bottom: 0.9em">If the external
execution environment supports passing arguments to a program, then Argument
returns an implementation-defined value corresponding to the argument
at relative position Number. <A NAME="I6275"></A>If Number is outside
the range 1..Argument_Count, then Constraint_Error is propagated. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>14.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Ramification: </B>If the external
execution environment does not support passing arguments to a program,
then Argument(N) for any N will raise Constraint_Error, since Argument_Count
is 0.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>15</FONT></DIV>
<DIV Class="Examples"><TT><B>function</B> Command_Name <B>return</B> String;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>16</FONT></DIV>
<DIV Class="CodeIndented" Style="margin-bottom: 0.9em">If the external
execution environment supports passing arguments to a program, then Command_Name
returns an implementation-defined value corresponding to the name of
the command invoking the program; otherwise Command_Name returns the
null string.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>16.1/1</FONT></DIV>
<DIV Class="Examples"><TT><U><B>type</B> <A NAME="I6276"></A><A NAME="I6277"></A>Exit_Status <B>is</B> <I>implementation-defined integer type</I>;</U></TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>17</FONT></DIV>
<DIV Class="CodeIndented" Style="margin-bottom: 0.9em">The type Exit_Status
represents the range of exit status values supported by the external
execution environment. The constants Success and Failure correspond to
success and failure, respectively.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>18</FONT></DIV>
<DIV Class="Examples"><TT><B>procedure</B> Set_Exit_Status (Code : <B>in</B> Exit_Status);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>19</FONT></DIV>
<DIV Class="CodeIndented">If the external execution environment supports
returning an exit status from a program, then Set_Exit_Status sets Code
as the status. Normal termination of a program returns as the exit status
the value most recently set by Set_Exit_Status, or, if no such value
has been set, then the value Success. If a program terminates abnormally,
the status set by Set_Exit_Status is ignored, and an implementation-defined
exit status value is set.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>20</FONT></DIV>
<DIV Class="CodeIndented"><S><A NAME="I6278"></A></S>If the external
execution environment does not support returning an exit value from a
program, then Set_Exit_Status does nothing. </DIV>
<H4 ALIGN=CENTER>Implementation Permissions</H4>
<DIV Class="Paranum"><FONT SIZE=-2>21</FONT></DIV>
<DIV Class="Normal"> An alternative declaration is allowed for package
Command_Line if different functionality is appropriate for the external
execution environment. </DIV>
<DIV Class="NotesHeader"><FONT SIZE=-1>NOTES</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>22</FONT></DIV>
<DIV Class="Notes"><FONT SIZE=-1>36 Argument_Count, Argument,
and Command_Name correspond to the C language's argc, argv[n] (for n>0)
and argv[0], respectively. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>22.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>To be honest: </B>The correspondence
of Argument_Count to argc is not direct -- argc would be one more than
Argument_Count, since the argc count includes the command name, whereas
Argument_Count does not. </FONT></DIV>
<H4 ALIGN=CENTER>Extensions to Ada 83</H4>
<DIV Class="Paranum"><FONT SIZE=-2>22.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><A NAME="I6279"></A>This clause
is new in Ada 95. </FONT></DIV>
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