How do I find matching filenames in a directory listing?

Here's how to do it with grep, using Perl regular expression syntax -P, and the return-only-matching-part switch -o:

grep -Poi "(.*pictures.*\.iso.*pictures.*|.*pictures.*\.iso|.*pictures.*)"  | sort | uniq

which returns:

OS Backups.iso, background/pictures.jpg
Pictures vacation 2011.iso

• for each line, grep first checks if it's an .iso files with "pictures" in its name, which also contains a file with "pictures" in its name, e.g.:

  Pictures vacation 2011.iso, italy/pictures5.jpg

• If it finds, it prints the line and moves on; if not, it checks if this is an .iso files with "pictures" in its name;
• If so, it prints just the ISO name; if not, it checks if this line contains a file with "pictures" in its name...

$ awk -F ", " 'BEGIN { IGNORECASE=1 } $1 ~ /pictures/ { print $1 ; next } $2 ~ /pictures/ { print }' < context.txt | sort | uniq
OS Backups.iso, background/pictures.jpg
Pictures vacation 2011.iso

#!/usr/bin/env python

import re, sys
a_file = sys.argv[1]
a_string = sys.argv[2]

#from http://www.peterbe.com/plog/uniqifiers-benchmark
def uniquify(seq, idfun=None): 
   # order preserving
   if idfun is None:
       def idfun(x): return x
   seen = {}
   result = []
   for item in seq:
       marker = idfun(item)
       # in old Python versions:
       # if seen.has_key(marker)
       # but in new ones:
       if marker in seen: continue
       seen[marker] = 1
       result.append(item)
   return result

mylist = []

with open(a_file, 'r') as items:
    for line in items.readlines():
        if (re.search(a_string, line, re.IGNORECASE)):
            temp = line.split(',',1)
            if (re.search(a_string, temp[0], re.IGNORECASE)):
                mylist.append(temp[0])
            else:
                mylist.append(line.rstrip())

mylist = uniquify(mylist)
for item in mylist:
    print(item)

Produces the desired output when run as python test.py index.txt pictures

import fileinput
import sys
lookFor = sys.argv[1]
for line in fileinput.input("textfile.txt"):
    if lookFor in line:
            print line

You can run this script with python scriptName.py WORDTOLOOKFOR For example, if I want to check for a line in the textfile containing the word "ubuntu", and the script is named script.py I write the following

python script.py ubuntu

Be sure to rename the textfile in the script.

Edit: This will only print the lines containing it, not store it anywhere, much like what grep can do.