Searching text file for a string in a fixed position

[229257]

Hi,
I was wondering if someone could help me? I want to search through a text file looking for a certain string just like you would with 'grep' but i only want to return results if the string pattern appears in a fixed position on the file.

E.g. i want to searh for a username in the passwd file e.g. 'adj' but i only want the line to be returned if this username appears at character positions 1 to 3.

Is there such a command or method that could do this for me?
Thanks
00229257

 

[p5wizard]

grep '^adj' /etc/passwd

HTH,

p5wizard

 

[229257]

That works great but how could how could search for that string in a different position e.g. positions 6 to 8?

Thanks

229257

 

[p5wizard]

grep '^.....adj'

There is also an awk solution:

cat /etc/passwd|awk '{if (substr($0,6,3)=="adj") print}'

HTH,

p5wizard

 

[futurelet]

[tt]cat /etc/passwd|awk '{if (substr($0,6,3)=="adj") print}'[/tt]

[tt]cat[/tt] isn't needed. Even if [tt]Awk[/tt] couldn't read files, [tt]cat[/tt] wouldn't be needed, because one could say: [tt]awk '....' <myfile[/tt].

awk 'substr($0,6) ~ /^adj/' /etc/passwd

 

[229257]

In this case we needed to use a form of cat (ypcat);

ypcat passwd | awk '{if (substr($0,1,3)=="adj") print}'

Becuause we have several UNIX server's and the one we are using for this project is not the NIS controller.

ypcat either contacts the NIS controller or has a shadow copy of the passwd from the NIS controller.

 

[p5wizard]

@futurelet,

I KNOW that cat isn't needed, I just didn't want anyone to misread or mistype and OUTPUT TO /etc/passwd instead of reading from it...

Whenever a config file is being queried, I PREFER to use cat and pipe the output to a command if that command can't read the file itself. I'll take the overhead of one more process.


HTH,

p5wizard

 

[futurelet]

Since cat is needed, I believe this is an idiomatic Awk solution:

ypcat passwd | awk 'substr($0,6) ~ /^adj/'

[tt]{ if [/tt] and [tt] print } [/tt] aren't needed.