rtr is a command-line tool for text processing based on Python-like slice syntax.
slice is a mandatory argument that specifies a slice that will be used for text processing.
file is an optional argument that specifies a filename to read the input from. If it's omitted then the input will be read fromstdin.
Provides a way to perform text filtering and transformation based on a simple Python-like slice indexing.All the text could be treated like athree dimensional array where: each line represents a row (1D), each word in the line represents a column (2D), and each character in the word represents a depth (3D). For example this text:
-rw-r--r-- 1 4rtzel 4rtzel 134 May 6 11:24 Cargo.lock-rw-r--r-- 1 4rtzel 4rtzel 212 May 6 11:24 Cargo.tomldrwxr-xr-x 7 4rtzel 4rtzel 4.0K May 6 11:42 .git-rw-r--r-- 1 4rtzel 4rtzel 8 May 6 11:24 .gitignore-rw-r--r-- 1 4rtzel 4rtzel 1.1K May 6 11:24 LICENSEdrwxr-xr-x 3 4rtzel 4rtzel 4.0K May 6 11:24 srcdrwxr-xr-x 3 4rtzel 4rtzel 4.0K Apr 29 16:41 target
could be presented in the following grid:
| - | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|
| 0 | -rw-r--r-- | 1 | 4rtzel | 4rtzel | 134 | May | 6 | 11:24 | Cargo.lock |
| 1 | -rw-r--r-- | 1 | 4rtzel | 4rtzel | 212 | May | 6 | 11:24 | Cargo.toml |
| 2 | drwxr-xr-x | 7 | 4rtzel | 4rtzel | 4.0K | May | 6 | 11:42 | .git |
| 3 | -rw-r--r-- | 1 | 4rtzel | 4rtzel | 8 | May | 6 | 11:24 | .gitignore |
| 4 | -rw-r--r-- | 1 | 4rtzel | 4rtzel | 1.1K | May | 6 | 11:24 | LICENSE |
| 5 | drwxr-xr-x | 3 | 4rtzel | 4rtzel | 4.0K | May | 6 | 11:24 | src |
| 6 | drwxr-xr-x | 3 | 4rtzel | 4rtzel | 4.0K | Apr | 29 | 16:41 | target |
and each cell will have an additional dimensional for characters.
We then could use a Python-like slice indexing to extract the text that we want. The indexing syntax looks like that:
range =<from>:<to>:<step>slice = range,range,range
<from> -- first index to extract text from (e.g.20: will extract text from index 20 onward).<to> -- last index to extract text from (e.g.:30 will extract all text before index 31).<step> -- step to use for text extraction (e.g.::2 will extract every second index).
from andto could have negative values. In that case, the actual number will be calculated by subtracting this value from the input's length(e.g.-5: means the fifth index from the end).
step could also be negative (but not 0). In that case, the output will be reversed(e.g.::-2 for step means to reverse the output and extract every second word).
All these indexes have default values and thus could be omitted. The default values are the following:
Additionally, each range could be prefixed with "!" to exclude this particular range. So!1:3 will output every line except for lines from 1 to 3.
Another example: if you want to print only the first and the last line one could use:!1:-2.
We'll be using the following input for all examples belove:
$ ll /proc| tail -20dr-xr-xr-x 5 root root 0 May 6 12:54 pressure-r--r--r-- 1 root root 0 May 6 12:54 sched_debug-r--r--r-- 1 root root 0 May 6 12:54 schedstatdr-xr-xr-x 4 root root 0 May 6 12:54 scsilrwxrwxrwx 1 root root 0 Mar 29 14:00 self -> 2658052-r-------- 1 root root 0 May 6 12:54 slabinfo-r--r--r-- 1 root root 0 May 6 12:18 softirqs-r--r--r-- 1 root root 0 May 6 12:18 stat-r--r--r-- 1 root root 0 Mar 29 14:00 swapsdr-xr-xr-x 1 root root 0 Mar 29 14:00 sys--w------- 1 root root 0 May 6 12:54 sysrq-triggerdr-xr-xr-x 5 root root 0 May 6 12:54 sysvipclrwxrwxrwx 1 root root 0 Mar 29 14:00 thread-self -> 2658052/task/2658052-r-------- 1 root root 0 May 6 12:54 timer_listdr-xr-xr-x 6 root root 0 May 6 12:54 tty-r--r--r-- 1 root root 0 May 6 12:18 uptime-r--r--r-- 1 root root 0 May 6 12:54 version-r-------- 1 root root 0 May 6 12:54 vmallocinfo-r--r--r-- 1 root root 0 May 6 12:54 vmstat-r--r--r-- 1 root root 0 May 6 12:54 zoneinfo
in the following way:
ll /proc| tail -20| rtr<slice>
Print all lines from line 15:
$ ll /proc| tail -20| rtr 15:-r--r--r-- 1 root root 0 May 6 12:18 uptime-r--r--r-- 1 root root 0 May 6 12:54 version-r-------- 1 root root 0 May 6 12:54 vmallocinfo-r--r--r-- 1 root root 0 May 6 12:54 vmstat-r--r--r-- 1 root root 0 May 6 12:54 zoneinfo
Print first 3 lines (indexes start at 0):
$ ll /proc| tail -20| rtr :2dr-xr-xr-x 5 root root 0 May 6 12:54 pressure-r--r--r-- 1 root root 0 May 6 12:54 sched_debug-r--r--r-- 1 root root 0 May 6 12:54 schedstat
Print lines from 10 to 12:
$ ll /proc| tail -20| rtr 10:12--w------- 1 root root 0 May 6 12:54 sysrq-triggerdr-xr-xr-x 5 root root 0 May 6 12:54 sysvipclrwxrwxrwx 1 root root 0 Mar 29 14:00 thread-self -> 2658052/task/2658052
Print last 3 lines:
$ ll /proc| tail -20| rtr -3:-r-------- 1 root root 0 May 6 12:54 vmallocinfo-r--r--r-- 1 root root 0 May 6 12:54 vmstat-r--r--r-- 1 root root 0 May 6 12:54 zoneinfo
From the last 5 lines print the first 2:
$ ll /proc| tail -20| rtr -5:-4-r--r--r-- 1 root root 0 May 6 12:18 uptime-r--r--r-- 1 root root 0 May 6 12:54 version
Print only line 10:
$ ll /proc| tail -20| rtr 10--w------- 1 root root 0 May 6 12:54 sysrq-trigger
Print every 4th line:
$ ll /proc| tail -20| rtr ::4dr-xr-xr-x 5 root root 0 May 6 12:54 pressurelrwxrwxrwx 1 root root 0 Mar 29 14:00 self -> 2658052-r--r--r-- 1 root root 0 Mar 29 14:00 swapslrwxrwxrwx 1 root root 0 Mar 29 14:00 thread-self -> 2658052/task/2658052-r--r--r-- 1 root root 0 May 6 12:54 version
Print lines from 10 to 15 with the step of 2 reversed:
$ ll /proc| tail -20| rtr 10:15:-2-r--r--r-- 1 root root 0 May 6 12:18 uptime-r-------- 1 root root 0 May 6 12:54 timer_listdr-xr-xr-x 5 root root 0 May 6 12:54 sysvipc
Print only the last word in each line:
$ ll /proc| tail -20| rtr ,-1pressuresched_debugschedstatscsi2658052slabinfosoftirqsstatswapssyssysrq-triggersysvipc2658052/task/2658052timer_listttyuptimeversionvmallocinfovmstatzoneinfo
Print last 3 lines but the words are reversed:
$ ll /proc| tail -20| rtr -3:,::-1vmallocinfo 12:54 6 May 0 root root 1 -r--------vmstat 12:54 6 May 0 root root 1 -r--r--r--zoneinfo 12:54 6 May 0 root root 1 -r--r--r--
Reverse all characters in each word in line 1:
$ ll /proc| tail -20| rtr 0,,::-1x-rx-rx-rd 5 toor toor 0 yaM 6 45:21 erusserp
Reverse the whole first line:
$ ll /proc| tail -20| rtr 0,::-1,::-1erusserp 45:21 6 yaM 0 toor toor 5 x-rx-rx-rd
Print only the first character in each word for the last line:
$ ll /proc| tail -20| rtr -1,,0- 1 r r 0 M 6 1 z
Print only the first and the last word in the last three lines:
$ ll /proc| tail -20| rtr'-3:,!1:-2'-r-------- vmallocinfo-r--r--r-- vmstat-r--r--r-- zoneinfo