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I have created a script that allows the user to select a file by copying and pasting that file. Then perform a grep on that file. I want to know is it possible to put a number in front of each files in the directory so the user will only have to type a number.

What I have tried:

  • Do ls -l then ls | wc -l then have the user select the corresponding file number, no luck.
  • Next, ls -i, tried to perform a grep using the node number for that file, no luck.
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This is an ideal use for bash arrays. – technosaurus Aug 1 '12 at 13:46
1  
Obligatory warning about parsing ls output - know the dangers before attempting to rely on it. – jw013 Aug 1 '12 at 14:32

3 Answers

up vote 7 down vote

In bash, ksh and zsh you can use the select keyword for that:

select file in *; do
  grep 'something' "$file"
done

To give the use instruction while the select list is displayed, set $PS3 before running select, for example:

PS3='number of file to grep in, ^C to exit: '
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1  
+1, but this sends you into a loop selecting files. To do this only one time use a break before done. This also works in zsh. – bahamat Aug 1 '12 at 16:09
Thanks for the zsh note, @bahamat. – manatwork Aug 1 '12 at 16:22
1  
The loop will exit when it sees EOF, so use ^D to exit. ^C will abort your script, which may not be what you want. – Starfish Aug 1 '12 at 18:27
Good point, @Starfish. – manatwork Aug 1 '12 at 18:35
That is, if you want to leave it up to the user. – bahamat Aug 1 '12 at 19:46
up vote 1 down vote

For putting the line numbers in front of ls, it may be easiest to

 ls -1 | cat -n

Then to select file number N, you could try

ls -1 | sed -n Np
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There is also ls -1 | nl. – scai Aug 1 '12 at 12:51
3  
Also, -1 option to ls is implicit when output goes to a pipe. – enzotib Aug 1 '12 at 13:02
1  
In case between ls|cat and ls|sed some new files appear in dir it may select wrong file. – rush Aug 1 '12 at 15:08
@rush One shouldn't store the selected number but the filename belonging to this number. – scai Aug 1 '12 at 16:32
up vote 0 down vote

By the way, you can use inode number and do it with only ls:

ls -i

will output something like: 

 $ ls -i
13107210 file
13238318 dir
13109301 script.sh

However the number is pretty big comparing to cat -n. But the main advantage of this way is that you always will find the exact file, while with cat -n + sed you can take another if between two command some new files were created in your dir.

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I tried the ls -i option with no luck. Is it possible to grep the file using the inode number? What would be the command? – user1545938 Aug 7 '12 at 10:09
the best way to find file with exact inode is to use find : find . -inum INODE_NUM . Is this what are you talking about? – rush Aug 7 '12 at 10:29
After trying to put a number in front of the file with the ls command. I looked into the ls -i command. In my script I did the – user1545938 Aug 8 '12 at 11:51
Sorry about that. I'll posted the script. I'm going to try the steps Bernhard posted. Thanks for all the good information. – user1545938 Aug 8 '12 at 12:02
Btw, if you explain properly what's going wrong, I'll be able to help you. – rush Aug 8 '12 at 12:08
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