User's Manual

acosh.o //Object modules are displayed.
erf.o
fabs.o
. . . .
This indicates that the library was built from object files named acosh.o, erf.o, fabs.o, and
so forth. In other words, module names are the same as the names of the object files from
which they were created.
Example of Creating an Archive Library
Suppose you are working on a program that does several conversions between English and Metric
units. The routines that do the conversions are contained in three C-language files. Following are
the three C-language files:
length.c - Routine to Convert Length Units
float in_to_cm(float in) /* convert inches to centimeters */
{
return (in * 2.54);
}
volume.c - Routine to Convert Volume Units
float gal_to_l(float gal) /* convert gallons to liters */
{
return (gal * 3.79);
}
mass.c - Routine to Convert Mass Units
float oz_to_g(float oz) /* convert ounces to grams */
{
return (oz * 28.35);
}
During development, each routine is stored in a separate file. To make the routines easily accessible
to other programmers, they must be stored in an archive library. To do this, first compile the source
files, either separately or together on the same command line:
$ cc -Aa -c length.c volume.c mass.c Compile them together.
length.c:
volume.c:
mass.c:
$ ls *.o List the .o files.
length.o mass.o volume.o
Then combine the .o files by running ar with the r key, followed by the library name (say libunits.a),
followed by the names of the object files to place in the library:
$ ar r libunits.a length.o volume.o mass.o
ar: creating libunits.a
To verify that ar created the library correctly, view its contents:
$ ar t libunits.a Use ar with the t key.
length.o
volume.o
mass.o All the .o modules are included; it worked.
Now suppose you have written a program, called convert.c, which calls several of the routines in
the libunits.a library. You can compile the main program and link it to libunits.a with the
following cc command:
$ cc -Aa convert.c libunits.a
96 Creating and Using Libraries