To find/replace a string in all current directory files and sub directory files

grep -i test $(find . -name "*.txt")

sample output :
$ grep -i test $(find . -name "*.txt")
./apiclasses_all.txt:atg.commerce.order.processor.ProcValidateStoreCredit

you can also try with

$ find . -name "*.txt" -exec grep -i test {} \; -print

atg.commerce.order.processor.ProcValidateStoreCredit
./apiclasses_all.txt

In some environments grep with recursive will work

$ grep -r -i raj *.txt

test1.txt:raj
text2.txt:raj

If there are many instances running on same machine and logs are redirecting to same directory
for example:

$ ls -ltr
total 1779040
-rw-r--r--   1 sr8879   sysadmin    6243 Aug  5 10:42 jdbc.rar
drwxr-xr-x   2 root     root         178 Aug 26 16:29 hsperfdata_root
drwx------   2 root     root         117 Aug 26 16:30 vx.004203.035257.110400.1642
drwx------   2 root     root         117 Aug 26 16:30 vx.106663.005702.043400.1753
drwx------   2 root     root         117 Aug 26 16:30 vx.113510.132240.132400.1883
-rw-------   1 root     other        133 Aug 26 16:30 sh22020
-rw-------   1 root     other        430 Aug 26 16:30 croutAAA4Aaisc
-rw-r--r--   1 wlsadmin atg       203422 Aug 27 05:07 dynolog.PREMIERQA1CAAPP-20100827050632
-rw-r--r--   1 wlsadmin atg       352234 Aug 27 05:14 PQACAMAIN1logs.txt.3326163321
-rw-r--r--   1 wlsadmin atg       179579 Aug 27 05:14 PQACASTAGlogs.txt.3326163343
-rw-r--r--   1 wlsadmin atg       892162 Aug 27 16:18 PQACAMAIN1logs.txt.1427051427
-rw-r--r--   1 wlsadmin atg       178808 Aug 27 16:19 PQACASTAGlogs.txt.1427051449
-rw-r--r--   1 wlsadmin atg       172779 Aug 27 16:52 dynolog.PREMIERQA1CAAPP-20100827165130

you want to search for error containing "repository does not have SELECT permission" only in Staging logs
PQACASTAG* logs belongs to Staging instance
So inorder to search those logs

To get only PQACASTAG* logs
by using grep and sed

$ ls -ltr | grep -i 'PQACASTAG*' | sed 's/^.*PQA/PQA/g'

PQACASTAGlogs.txt.3326163343
PQACASTAGlogs.txt.1427051449
PQACASTAGlogs.txt.5927165947

or  by using awk and grep

$ ls -ltr | awk '{print $9}' | grep -i 'PQACASTAG*'

PQACASTAGlogs.txt.3326163343
PQACASTAGlogs.txt.1427051449
PQACASTAGlogs.txt.5927165947

Now we need to search only those logs

$ grep -i error.*select.*permission $(ls -ltr | awk '{print $9}' | grep -i 'PQACASTAG*')

PQACASTAGlogs.txt.3326163343:**** Error Thu Aug 26 16:51:57 PDT 2010    1282866717694   /com/att/wireless/reporting/ReportingRepository      The table: "V_ONLINE_ORDER_INFO" does not appear to be defined correctly in the database. Either the table does not exist, the repository does not have SELECT permission on it, or the definition of the table is incompatible with the template in use.

PQACASTAGlogs.txt.3326163343:**** Error Thu Aug 26 16:51:57 PDT 2010    1282866717701   /com/att/wireless/reporting/ReportingRepository      The table: "V_ONLINE_ORDER_STATUS_INFO" does not appear to be defined correctly in the database. Either the table does not exist, the repository does not have SELECT permission on it, or the definition of the table is incompatible wit
h the template in use.


To replace all "text" in all ".txt" files in current directory

find . -name "*.txt" -exec sed -i 's/text/raj/g' {} \;
or
sed -i 's/raj/text/g' $(find . -name "*.txt")

  
Displaying all html's which contains a word as links in browser (more like a local search engine)

grep -il $1 $(find /cygdrive/c/ATGPlatform91docs/ -name "*.htm[l]" -type f) | sed 's/\(.*\)/\1<\/a>
/g' > search.html; links search.html

to use
./satg Repository
which will display results in links browser with all html's as links which contains"Repository".
You can either use links or lynx or firefox to view search.html