An awk program consists of a sequence of zero or more pattern-action
statements and optional function definitions. One or the other of the
pattern and action may be omitted.
pattern { action statements }
pattern
{ action statements }
function name(parameter list) { action statements }
gawk first reads the program source from the
program-file(s), if specified, or from the first non-option
argument on the command line. The `-f' option may be used multiple
times on the command line. gawk reads the program text from all
the program-file files, effectively concatenating them in the
order they are specified. This is useful for building libraries of
awk functions, without having to include them in each new
awk program that uses them. To use a library function in a file
from a program typed in on the command line, specify
`--source 'program'', and type your program in between the single
quotes.
See section Command Line Options.
The environment variable AWKPATH specifies a search path to use
when finding source files named with the `-f' option. The default
path, which is
`.:/usr/local/share/awk'(27) is used if AWKPATH is not set.
If a file name given to the `-f' option contains a `/' character,
no path search is performed.
See section The AWKPATH Environment Variable.
gawk compiles the program into an internal form, and then proceeds to
read each file named in the ARGV array.
The initial values of ARGV come from the command line arguments.
If there are no files named
on the command line, gawk reads the standard input.
If a "file" named on the command line has the form `var=val', it is treated as a variable assignment: the variable var is assigned the value val. If any of the files have a value that is the null string, that element in the list is skipped.
For each record in the input, gawk tests to see if it matches any
pattern in the awk program. For each pattern that the record
matches, the associated action is executed.
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