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updated documentation a bit

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hyung-hwan 2020-03-16 08:28:02 +00:00
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@ -121,6 +121,7 @@ The regular expression `/abc/` matches the first input line and `/stu/` matches
third input line. So the range is true between the first input line and the
third input line inclusive.
### Entry Point
The typical execution begins with the BEGIN block, goes through pattern-action blocks, and eaches the END block. If you like to use a function as an entry point, you may set a function name with @pragma entry.
@ -133,6 +134,99 @@ The typical execution begins with the BEGIN block, goes through pattern-action b
}
### Pragmas
Besides the entry pragma, there are other prgrma available.
A pragma item of the file scope can be placed in any source files.
A pragma item of the global scope can appear only once thoughout the all source files.
| Name | Scope | Values | Description |
|---------------|--------|---------------|--------------------------------------------------------|
| implicit | file | on, off | allow undeclared variables |
| multilinestr | file | on, off | allow a multiline string literal without continuation |
| entry | global | function name | change the program entry point |
| striprecspc | global | on, off | |
| striprecspc | global | on, off | trim leading and trailing spaces when convering a string to a number |
### @include and @include_once
The @include directive inserts the contents of the file specified in the following string as if they appeared in the source stream being processed.
Assuming the hello.inc file contains the print_hello() function as shown below,
function print_hello() { print "hello\n"; }
You may include the the file and use the function.
@include "hello.inc";
BEGIN { print_hello(); }
The semicolon after the included file name is optional. You could write @include "hello.inc" without the ending semicolon.
@include_once is similar to @include except it doesn't include the same file multiple times.
@include_once "hello.inc";
@include_once "hello.inc";
BEGIN { print_hello(); }
In this example, print_hello() is not included twice.
You may use @include and @include_once inside a block as well as at the top level.
BEGIN {
@include "init.inc";
...
}
### Comments
Hawk supports a single-line commnt that begins with a hash sign # and the C-style multi-line comment.
x = y; # assign y to x.
/*
this line is ignored.
this line is ignored too.
*/
### Reserved Words
The following words are reserved and cannot be used as a variable name, a parameter name, or a function name.
- @abort
- @global
- @include
- @include_once
- @local
- @pragma
- @reset
- BEGIN
- END
- break
- continue
- delete
- do
- else
- exit
- for
- function
- getbline
- getline
- if
- in
- next
- nextfile
- nextofile
- print
- printf
- return
- while
However, these words can be used as normal names in the context of a module call. For example, mymod::break. In practice, the predefined names used for built-in commands, functions, and variables are treated as if they are reserved since you can't create another denifition with the same name.
### Values
- unitialized value
@ -159,22 +253,284 @@ A regular expression literal is special in that it never appears as an indendent
For this reason, there is no way to get the type name of a regular expressin literal.
### Pragmas
A pragma item of the file scope can be placed in any source files.
A pragma item of the global scope can appear only once thoughout the all source files.
### Numbers ###
| Name | Scope | Values | Description |
|---------------|--------|---------------|--------------------------------------------------------|
| implicit | file | on, off | allow undeclared variables |
| multilinestr | file | on, off | allow a multiline string literal without continuation |
| entry | global | function name | change the program entry point |
| striprecspc | global | on, off | |
| striprecspc | global | on, off | trim leading and trailing spaces when convering a string to a number |
An integer begins with a numeric digit between 0 and 9 inclusive and can be
followed by more numeric digits. If an integer is immediately followed by a
floating point, and optionally a series of numeric digits without whitespaces,
it becomes a floting-point number. An integer or a simple floating-point number
can be followed by e or E, and optionally a series of numeric digits with a
optional single sign letter. A floating-point number may begin with a floting
point with a preceeding number.
369 # integer
3.69 # floating-pointe number
13. # 13.0
.369 # 0.369
34e-2 # 34 * (10 ** -2)
34e+2 # 34 * (10 ** 2)
34.56e # 34.56
34.56E3
An integer can be prefixed with 0x, 0, 0b for a hexa-decimal number, an octal
number, and a binary number respectively. For a hexa-decimal number, letters
from A to F can form a number case-insenstively in addition to numeric digits.
0xA1 # 161
0xB0b0 # 45232
020 # 16
0b101 # 5
If the prefix is not followed by any numeric digits, it is still a valid token
and represents the value of 0.
0x # 0x0 but not desirable.
0b # 0b0 but not desirable.
### Module
Hawk supports various modules.
#### String
The *str* module provides an extensive set of string manipulation functions.
- str::gsub - equivalent to gsub
- str::index
- str::isalnum
- str::isalpha
- str::isblank
- str::iscntrl
- str::isdigit
- str::isgraph
- str::islower
- str::isprint
- str::ispunct
- str::isspace
- str::isupper
- str::isxdigit
- str::length - equivalent to length
- str::ltrim
- str::match - equivalent to match
- str::normspace
- str::printf - equivalent to sprintf
- str::rindex
- str::rtrim
- str::split - equivalent to split
- str::sub - equivalent to sub
- str::substr - equivalent to substr
- str::tolower - equivalent to tolower
- str::tonum - convert a string to a number. a numeric value passed as a parameter is returned as it is. the leading prefix of 0b, 0, and 0x specifies the radix of 2, 8, 16 repectively. conversion stops when the end of the string is reached or the first invalid character for conversion is encountered.
- str::toupper - equivalent to toupper
- str::trim
- str::value - get the numeric value of the first character
#### System
The *sys* module provides various functions concerning the underlying operation system.
- sys::chmod
- sys::close
- sys::closedir
- sys::dup
- sys::errmsg
- sys::fork
- sys::getegid
- sys::getenv
- sys::geteuid
- sys::getgid
- sys::getpid
- sys::getppid
- sys::gettid
- sys::gettime
- sys::getuid
- sys::kill
- sys::mkdir
- sys::mktime
- sys::open
- sys::opendir
- sys::openfd
- sys::pipe
- sys::read
- sys::readdir
- sys::setttime
- sys::sleep
- sys::strftime
- sys::system
- sys::unlink
- sys::wait
- sys::write
You may read the file in raw bytes.
BEGIN {
f = sys::open("/etc/sysctl.conf", sys::O_RDONLY);
while (sys::read(f, x, 10) > 0) printf (B"%s", x);
sys::close (f);
}
You can map a raw file descriptor to a handle created by this module and use it.
BEGIN {
a = sys::openfd(1);
sys::write (a, B"let me write something here\n");
sys::close (a, sys::C_KEEPFD); ## set C_KEEPFD to release 1 without closing it.
##sys::close (a);
print "done\n";
}
Creating pipes and sharing them with a child process is not big an issue.
BEGIN {
if (sys::pipe(p0, p1, sys::O_CLOEXEC | sys::O_NONBLOCK) <= -1)
##if (sys::pipe(p0, p1, sys::O_CLOEXEC) <= -1)
##if (sys::pipe(p0, p1) <= -1)
{
print "pipe error";
return -1;
}
a = sys::fork();
if (a <= -1)
{
print "fork error";
sys::close (p0);
sys::close (p1);
}
else if (a == 0)
{
## child
printf ("child.... %d %d %d\n", sys::getpid(), p0, p1);
sys::close (p1);
while (1)
{
n = sys::read (p0, k, 3);
if (n <= 0)
{
if (n == sys::RC_EAGAIN) continue; ## nonblock but data not available
if (n != 0) print "ERROR: " sys::errmsg();
break;
}
print k;
}
sys::close (p0);
return 123;
}
else
{
## parent
printf ("parent.... %d %d %d\n", sys::getpid(), p0, p1);
sys::close (p0);
sys::write (p1, B"hello");
sys::write (p1, B"world");
sys::close (p1);
##sys::wait(a, status, sys::WNOHANG);
while (sys::wait(a, status) != a);
if (sys::WIFEXITED(status)) print "Exit code: " sys::WEXITSTATUS(status);
else print "Child terminated abnormally"
}
}
BEGIN {
if (sys::pipe(p0, p1, sys::O_NONBLOCK | sys::O_CLOEXEC) <= -1)
{
print "pipe error";
return -1;
}
a = sys::fork();
if (a <= -1)
{
print "fork error";
sys::close (p0);
sys::close (p1);
}
else if (a == 0)
{
## child
sys::close (p0);
stdout = sys::openfd(1);
sys::dup(p1, stdout);
print B"hello world";
print B"testing sys::dup()";
print B"writing to standard output..";
sys::close (p1);
sys::close (stdout);
}
else
{
sys::close (p1);
while (1)
{
n = sys::read(p0, k, 10);
if (n <= 0)
{
if (n == sys::RC_EAGAIN) continue; ## nonblock but data not available
if (n != 0) print "ERROR: " sys::errmsg();
break;
}
print "[" k "]";
}
sys::close (p0);
sys::wait(a);
}
}
You can duplicate file handles as necessary.
BEGIN {
a = sys::open("/etc/inittab", sys::O_RDONLY);
x = sys::open("/etc/fstab", sys::O_RDONLY);
b = sys::dup(a);
sys::close(a);
while (sys::read(b, abc, 100) > 0) printf (B"%s", abc);
print "-------------------------------";
c = sys::dup(x, b, sys::O_CLOEXEC);
## assertion: b == c
sys::close (x);
while (sys::read(c, abc, 100) > 0) printf (B"%s", abc);
sys::close (c);
}
Directory traversal is easy.
BEGIN {
d = sys::opendir("/etc", sys::DIR_SORT);
if (d >= 0)
{
while (sys::readdir(d,a) > 0)
{
sys::stat(a, b);
for (i in b) print i, b[i]; }
}
sys::closedir(d);
}
}
Socket functions are available.
BEGIN
{
s = sys::socket();
...
sys::close (s);
}
### Incompatibility with AWK
#### Parameter passing