Print and sort the login names of all users:
????????BEGIN???{ FS = ":" } ????????????????{ print $1 | "sort" }
Count lines in a file:
????????????????{ nlines++ } ????????END?????{ print nlines }
Precede each line by its number in the file:
????????{ print FNR,$0 }
Concatenate and line number (a variation on a theme):
????????{ print NR,$0 } Run an external command for particular lines of data:
????????tail -f access_log | ????????awk ’/myhome.html/ { system("nmap " $1 ">> logdir/myhome.html") }’
String constants are sequences of characters enclosed in double quotes. In non-English speaking environments,it is possible to mark strings in the?AWK?program as requiring translation to the native natural language. Such strings are marked in the?AWK?program with a leading underscore (‘‘_’’). For example,
gawk ’BEGIN { print "hello,world" }’
always prints?hello,world. But,
gawk ’BEGIN { print _"hello,world" }’
might print?bonjour,monde?in France.
There are several steps involved in producing and running a localizable?AWK?program.
| Description |
? ?BEGIN { TEXTDOMAIN = "myprog" }
This allows?gawk?to find the?.mo?file associated with your program. Without this step,?gawk?uses the?messages?text domain,which likely does not contain translations for your program.
myprog.po?to generate a.po?file for your program.The internationalization features are described in full detail in?GAWK: Effective AWK Programming.
A primary goal for?gawk?is compatibility with the?POSIX?standard,as well as with the latest version of?UNIX?awk. To this end,?gawk?incorporates the following user visible features which are not described in the?AWK?book,but are part of the Bell Laboratories version of?awk,and are in the?POSIX?standard.
The book indicates that command line variable assignment happens when?awk?would otherwise open the argument as a file,which is after the?BEGIN?block is executed. However,in earlier implementations,when such an assignment appeared before any file names,the assignment would happen?before?the?BEGIN?block was run. Applications came to depend on this ‘‘feature.’’ When?awk?was changed to match its documentation,the?-v?option for assigning variables before program execution was added to accommodate applications that depended upon the old behavior. (This feature was agreed upon by both the Bell Laboratories and the?GNU?developers.)
The?-W?option for implementation specific features is from the?POSIX?standard.
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