Category:TXR: Difference between revisions

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TXR is a new text extraction language implemented in C, running on Linux (and possibly other POSIX platforms).

Here is a very basic hello-world-type TXR query that re-implements the "free" utility:

<lang txr>#!/usr/bin/txr -f @(next "/proc/meminfo") @(skip) MemTotal:@/ +/@TOTAL kB MemFree:@/ +/@FREE kB Buffers:@/ +/@BUFS kB Cached:@/ +/@CACHED kB @(skip) SwapTotal:@/ +/@SWTOT kB SwapFree:@/ +/@SWFRE kB @(next `!echo $(( @TOTAL - @FREE ))`) @USED @(next `!echo $(( @USED - @BUFS - @CACHED ))`) @RUSED @(next `!echo $(( @FREE + @BUFS + @CACHED ))`) @RFREE @(next `!echo $(( @SWTOT - @SWFRE ))`) @SWUSE @(output)

              TOTAL         USED         FREE      BUFFERS       CACHED

Mem: @{TOTAL -12} @{USED -12} @{FREE -12} @{BUFS -12} @{CACHED -12} +/- buffers/cache: @{RUSED -12} @{RFREE -12} Swap: @{SWTOT -12} @{SWUSE -12} @{SWFRE -12} @(end)</lang>

Sample run:

$ ./meminfo.txr
               TOTAL         USED         FREE      BUFFERS       CACHED
Mem:          769280       647752       121528       160108       286844
+/- buffers/cache:         200800       568480
Swap:        1048568        18200      1030368

Arithmetic is not implemented in TXR as of version 035. The above example simply continues the pattern matching across invocations of echo to borrow the shell to do math. The command

@(next `!echo $(( @TOTAL - @FREE ))`)
@USED

means, "Next, please switch to scanning the output of this echo command with some variables substituted in. Then capture entire first line of this command into the USED variable."

Subcategories

This category has the following 3 subcategories, out of 3 total.

@

Pages in category "TXR"

The following 160 pages are in this category, out of 160 total.

1

100 doors

9

99 bottles of beer

A

B

D

E

F

G

H

I

J

K

Keyboard input/Obtain a Y or N response

L

M

N

O

P

Q

Quine

R

T

U

V

W

X

XML/Input

Y

@@ Line 1: / Line 1: @@
-{{stub}}{{language}}
+{{stub}}{{language
+|site=http://www.nongnu.org/txr/}}
-TXR[http://www.nongnu.org/txr/] is a new text extraction language implemented in C, running on Linux (and possibly other POSIX platforms).
+TXR is a new text extraction language implemented in [[C]], running on [[Linux]] (and possibly other [[POSIX]] platforms).
 Here is a very basic hello-world-type TXR query that re-implements the "free" utility:
@@ Line 45: / Line 46: @@
 </pre>
-means, "Next, please switch to scanning the output of this echo command with some variables substituted in.
+means, "Next, please switch to scanning the output of this echo command with some variables substituted in. Then capture entire first line of this command into the USED variable."
-Then capture entire first line of this command into the USED variable."