Vax 613 0S Instruction Manual download pdf (Page 21)

USER

GROUP

NEWS

Issue 3 - Vol 2

MDP

APPLICATIONS

INCLUDING

MATH

LIBRARIES

IN

NATIVE

C

PROGRAMS

Including

math

libraries

in

C programs with

the

optional

native

C package is

not

automatic

with

the

normal

cc

invocation.

To

gain access to

the

math

functions, use

the

-1m

option on

the

command

line.

The

following exam-

ple shows how

t.o

compile and

run

a

short

example using a square

root

function.

C program

'sqrt.c'

#include

<math.h>

mainO {

float

i=2.0;

printf(" sqrt(2.0) =

%I\n"

,sqrt(i));

}

Compilation:

cc

sqrt.c

-1m

Execution:

$ sqrt

sqrt(2.0) =

1.414214

$

The

-1m

option

is

not

documented

under"

cc"

because

it

is

a loader flag.

Use"

man

Id"

or

see"

Id" in section 6 of

the

TNIX

System Reference Manual.

When

used

with"

cc"

the

-1m

option

must

be

at

the

end

of

the

command

line.

Greg

Saville, Software Applications Manager

TNIX

COMMENT

LINES

ARE

NOT

IGNORED

In a

TNIX

command

file,

a line may become a

comment

by preceding

the

text

on

the

line

with

a

":

" (a colon

and

a space).

The

content

of a

commented

line however is still evaluated by the shell

and

then

ignored.

If

the

evalua-

tion uncovers

a problem,

the

execution

of

the

command

file

will be

terminated.

I

don't

want

this

line

executed.

The

above line

in

a

command

file

will fail due

to

the"

,,,

character in

the

line.

This feature

is

quite useful as

the

following example shows.

A

command

file

that

requires

three

parameters

be

passed

to

it

${1?}

${2?}

${3?}

MDL $1

$2

$3

If

the

command

is

invoked

without

all

parameters

being defined,

the

command

file

will fail and

exit

prior

to

exe-

cuting

the"

mdl"

command

and will

state

which

parameter

was missing.

The

TI\T]X

manual

section "Shell Programming" has a good description of

other

uses

of

the

"S{variable

- function

- variable} capability.

The

comment

line

"I

don't

want

this line executed" can be used as a

comment

if it

is

enclosed in quotes as shown

here.

Thus;

:

"I

don't

want

this line executed"

will

not

create a problem in a

command

file.

John Owens, Systems Applications

Manager

December 1983

TEKTRONIX

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