The function for writing to standard output is the print
function in the System module. Like C's printf
function, it provides formatted output through the use of fomat verbs.
sys->print("Hello, %s!\n", hd (tl argv));This uses the
%s
format verb to print the data contained in the head of the argv
list (which is a string), in addition to printing the literal string. For example:
Hello, Inferno!To direct the output to a device other than standard output, use the
fprint
function. This requires an additional parameter, an open FD
. For example, to print to standard error, use the fildes
function to obtain:
stderr := sys->fildes(2); # get the FD for stderr ... sys->fprint(stderr, "error: %s\n", msg);