Shell Programming and Scripting

Hi All,

This is my Scenario:
I wanted to check if a particular name or pattern is present in a file based of that rest of the program should proceed.
I want to print '0' if no matching found.

Code:

v_File_Count=`grep -i "$v_Name_Pattern" $File_Path/Master_File_List.txt | wc -l`

The above command is giving an output where a tab space is present due to which I am not able to do a condition.

Code:

 
 if [[ $v_File_Count == 0]]; then
 xyz...
 fi

Tried to remove the "<Tab Space>" as below but no use

Code:

 v_File_Count=`grep -i "$v_Name_Pattern" $File_Path/Master_File_List.txt | wc -l | tr "   " ""`
  
  
 ## Below code is not print any value if there is no record -- I want '0' if no record
 v_File_Count=`grep -i "$v_Name_Pattern" $File_Path/Master_File_List.txt | awk '{print NR}'`
 v_File_Count=`grep -i "$v_Name_Pattern" $File_Path/Master_File_List.txt | sed -n '$='`

Sample Input:
File = Master_File_List.txt

Code:

 abcd.txt
 xyz.txt
 lmno.txt

Command:

Code:

v_File_Count=`grep -i "$v_Name_Pattern" $File_Path/Master_File_List.txt | sed -n '$='

** Anycode

Expected Output: ( If there are no matching pattern, 0 should be returned i.e., v_File_Count should have value '0')

Do share your ideas and suggestion

perhaps try

Code:

tr -d '\t'

Not working.

Code:

Code:

grep -i "avc" $DNA_PARM/Master_Graph_List.csv | wc -l | tr -d '\t'

Ouptut:

Hi, try:

Code:

grep -ic "avc" $DNA_PARM/Master_Graph_List.csv

Regards.

These are actually two scenarios.

If you want to return the number of times a string is found within a file you take the "-c" ("count") option of grep:

Code:

# grep -c "text" /path/to/file_with_text_in.it
2

This would mean "text" is occurring in two lines of the file. To use it in a script:

Code:

iFoundNr=$(grep -c "<searchtext>" /path/to/file)

if [ $iFoundNr -eq 0 ] ; then
     echo "<searchtext>" was not found"
else
     echo "<searchtext> was found in $iFoundNr lines"
fi

But i suspect that you created the variable just because you weren't able to imagine a simpler way. Basically you want to do one thing if the text is found (however often) and another thing if not, right? Well, here it goes: the grep utility returns an "error level", which you can use. "0" means the search text was found, different than 0 means it was not found. Because in shell programming "0" equals to "true" and non-"0" equals to "false" you can use the "-q" (quiet) option of grep to suppress all output of it and directly write:

Code:

if grep -q "<searchtext>" /path/to/file ; then
     do_found
else
     do_notfound
done

You haven't asked the question, but an additional warning: when using variable contents as search patterns for grep (or similar tools: awk, sed, ...) take into account that some characters have a special meaning (they are so-called "meta-characters). The first of the following example will work as expected, the second one won't:

Code:

# search="abcd"         # this will work
# grep "$search" /path/to/file

# search="a[bc]d"       # this will work too, but not in the expected way
# grep "$search" /path/to/file

If you want to search for the string "a[bc]d" you need to "escape" metacharacters. To make the second example working (that is: searching for the fixed string "a[bc]d") you need to do that (notice the change in quoting too):

Code:

# search='a\[bc\]d'
# grep "$search" /path/to/file

I hope this helps.

bakunin

Thanks., OOO, I shall check and get back to you if further discussion/clarification required on this.

---------- Post updated 12-31-15 at 11:04 AM ---------- Previous update was 12-30-15 at 10:19 PM ----------

@ disedorgue @bakunin thanks, Working good.

@bakunin, additional information was helpful.