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awk Language
This manual describes the GNU implementation of awk, which is patterned
after the POSIX specification. Many awk users are only familiar
with the original awk implementation in Version 7 Unix, which is also
the basis for the version in Berkeley Unix (through 4.3--Reno). This chapter
briefly describes the evolution of the awk language.
The awk language evolved considerably between the release of
Version 7 Unix (1978) and the new version first made widely available in
System V Release 3.1 (1987). This section summarizes the changes, with
cross-references to further details.
awk Statements versus Lines).
return statement
(see section User-defined Functions).
delete statement (see section The delete Statement).
do-while statement
(see section The do-while Statement).
atan2, cos, sin, rand and
srand (see section Numeric Built-in Functions).
gsub, sub, and match
(see section Built-in Functions for String Manipulation).
close, which closes an open file, and
system, which allows the user to execute operating system
commands (see section Built-in Functions for Input/Output).
ARGC, ARGV, FNR, RLENGTH, RSTART,
and SUBSEP built-in variables (see section Built-in Variables).
awk
programs (see section Operator Precedence (How Operators Nest)).
FS
(see section Specifying how Fields are Separated), and as the
third argument to the split function
(see section Built-in Functions for String Manipulation).
getline function
(see section Explicit Input with getline).
BEGIN and END rules
(see section BEGIN and END Special Patterns).
The System V Release 4 version of Unix awk added these features
(some of which originated in gawk):
ENVIRON variable (see section Built-in Variables).
awk).
awk).
srand built-in function
(see section Numeric Built-in Functions).
toupper and tolower built-in string functions
for case translation
(see section Built-in Functions for String Manipulation).
printf function
(see section Using printf Statements for Fancier Printing).
"%*.*d")
in the argument list of the printf function
(see section Using printf Statements for Fancier Printing).
/foo/ as expressions, where
they are equivalent to use of the matching operator, as in $0 ~
/foo/ (see section Constant Expressions).
awk
The POSIX Command Language and Utilities standard for awk
introduced the following changes into the language:
CONVFMT for controlling the conversion of numbers
to strings (see section Conversion of Strings and Numbers).
gawk not in POSIX awk
The GNU implementation, gawk, adds these features:
AWKPATH environment variable for specifying a path search for
the `-f' command line option
(see section Invoking awk).
gawk specific features available via the `-W'
command line option (see section Invoking awk).
ARGIND variable, that tracks the movement of FILENAME
through ARGV. (see section Built-in Variables).
ERRNO variable, that contains the system error message when
getline returns -1, or when close fails.
(see section Built-in Variables).
IGNORECASE variable and its effects
(see section Case-sensitivity in Matching).
FIELDWIDTHS variable and its effects
(see section Reading Fixed-width Data).
next file statement for skipping to the next data file
(see section The next file Statement).
systime and strftime built-in functions for obtaining
and printing time stamps
(see section Functions for Dealing with Time Stamps).
awk).
awk).
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