UNIX for Dummies Questions & Answers

Hello everybody,

I would like to ask you, how to print first and last row from input (not file).
I want to get first and last name of file from directory sorted by name, which contains files e.g:
ab.txt
fg.txt
bc.txt

and the output should be ab.txt and fg.txt.

I used something like this

try this..

Code:

 find ./ -maxdepth 2 -mindepth 2 print | sort | awk -F"/" '{ if(NR ==1){print $NF }}END {print $NF}'

try this ; sort on the filename(here 9 is the column of the filename). It first sorts on the filename and prints the first and last lines.

Code:

 
ls -ltr | sort -nk9 | sed -n '1p;$p'

sparks partly got it right:

Code:

sed -n '1p;$p'

will print the first and last line of whatever comes its way: in a pipeline it prints the first and the last line of the input, given a filename it prints the first and last line of the file.

However: "sort -n" sorts numerically and with the filenames this does simply nothing because the aren't numerical values. The same goes for "sort -nk9", which sorts numerically on non-numerical input.

"ls" built-in default sorts ascending alphabetically, unless it is told other to do otherwise, like with "-r" (reverse the sorting order) and/or the "-t" (sort on timestamp). To switch off alphabetacal sorting to sort on timestamp descending ("-tr") first only to re-sort alphabetically later is somewhat futile, isn't it?

Code:

ls | sed -n '1p;$p'

will do what you want. You might ask why the output is in one column where the output of "ls" is in several columns. "ls" formats the output only in several columns if its output is going to a terminal. Still, you can force one-column-output with the "-1" switch and if you prefer long output use the "-l" switch. Write

Code:

ls -1 | sed -n '1p;$p'
ls -l | sed -n '1p;$p'

If you want to make sure to have only files (not directories, block devices, links, etc.) in your output you can filter them out in the long output easily:

Code:

ls -l | sed -n '/^-/p' | sed -n '1p;$p'

I hope this helps.

bakunin

wow, thank you all for your explanation.