Get line number using grep - tcl

Question

I would like to get the line number using grep command, but I am getting the error message when search pattern is not a single word:
couldn't read file "Pattern": no such file or directory
How should be the proper usage of the grep? The code is here:
set status [catch {eval exec grep -n '$textToGrep' $fileName} lineNumber]
if { $status != 0 } {
#error
} else {
puts "lineNumber = $lineNumber"
}
Also if the search pattern is not matched at all, the returned value is : "child process exited abnormally"
Here is the simple test case:
set textToGrep "<BBB name=\"BBBRM\""
file contents:
<?xml version="1.0"?>
<!DOCTYPE AAA>
<AAA>
<BBB name="BBBRM" />
</AAA>

Answer 1

Well, I also get problems with your code and a single word pattern!
First of all, I don't think you need the eval command, because catch itself does an evaluation of its first argument.
Then, the problem is that you put the $textToGrep variable in exec inside single quotes ', which have no meaning to Tcl.
Therefore, if the content of textToGrep is foo, you are asking grep to search for the string 'foo'. If that string, including the single quotes, is not found in the file, you get the error.
Try to rewrite your first line with
set status [catch {exec grep -n $textToGrep $fileName} lineNumber]
and see if it works. Also, read the exec man page, which explains well these problems.

Answer 2

If your system has tcllib install, you can use the fileutil::grep command from the fileutil package:
package require fileutil
set fileName data.xml
set textToGrep {<BBB +name="BBBRM"}; # Update: Add + for multi-space match
set grepResult [::fileutil::grep $textToGrep $fileName]
foreach result $grepResult {
# Example result:
# data.xml:4: <BBB name="BBBRM" />
set lineNumber [lindex [split $result ":"] 1]
puts $lineNumber
# Update: Get the line, squeeze the spaces before name=
set line [lindex [split $result ":"] 2]
regsub { +name=} $line " name=" line
puts $line
}
Discussion
When assigning value to textToGrep, I used the curly braces, thus allowing double quote inside without having to escape them.
the result of the ::fileutil::grep command is a lits of strings. Each string contains the file name, line number, and the line itself; separated by colon.
One way to extract the line number is to first split the string (result) into pieces, using the colon as a separator. Next, I use lindex to grab the second item (index=1, since list is zero-base).
I have updated the code to account for case where there are multiple spaces before name=

Answer 3

There are two problems here:
Pattern matching does not work.
grep exits with error child process
exited abnormally when pattern is not found
The first problem is because you are not enclosing the textToGrep within double quotes(instead of single quotes). So your code should be:
[catch {exec grep -n "$textToGrep" $fileName} lineNumber]
Second problem is because of the exit status of grep command. grep exits with error when the pattern is not found. Here is the try on a shell:
# cat file
pattern
pattern with multiple spaces
# grep pattern file
pattern
pattern with multiple spaces
# echo $?
0
# grep nopattern file
# echo $?
1
EDIT:
In your case you have special characters such as < and > (which have special meaning on a shell).
set textToGrep "<BBB name=\"BBBRM\""
regsub -all -- {<} "$textToGrep" "\\\<" textToGrep
regsub -all -- {>} "$textToGrep" "\\\>" textToGrep

Answer 4

set textToGrep {\<BBB name="BBBRM"}
catch {exec grep -n $textToGrep $fileName} status
if {![regexp "child process" $status]} {
puts $status
} else {
puts "no word found"
}
I think you should do regular expression with child process. Just check above code if it works. In if statement you can process the status command as you like.
With the given example (in your post) the above code works only you need to use backslash for the "<" in the textToGrep variable