18:31:30,788 access INFO request accepted. The word which I am trying to find is ––PWgJuTrmAX1A3jeoyAgAAAAADAQAX1AQUZm52OkJCMjg1QTQ But somehow grep is not returning the line which contains it. I am passing name of file from command line and also the word which I want to find through command line and print those lines which contains that word. I have a logfile say logfile.txt which contains info. Open(HANDLE, = grep /\Q$DeviceURI\E/, $subarray.”\n”
These conditioned matches should occur three times and one more class is mentioned separately. In the regular expression given above, there are different conditions. Oct 28 12:33:31 gstuff1 ntpd: synchronized to LOCAL(0), stratum 10 Oct 28 11:42:20 gstuff1 ntpd: synchronized to LOCAL(0), stratum 10 Now let us grep all the process Ids of ntpd daemon process using appropriate character class expression. These are always used inside square brackets in the form ]. Any alphanumeric character 0 to 9 OR A to Z or a to z. Refer man page of grep to know various character class expressions. Grep command supports some special character classes that denote certain common ranges. Character class expressionĪs we have seen in our previous regex article example 9, list of characters can be mentioned with in the square brackets to match only one out of several characters. $ grep -v "^#\|^'\|^\/\/" commentsĭouble slashes in the beginning of the line for single line comment in C.
Now the following grep command searches for the line which does not start with # or single quote (‘) or double front slashes (//). The file called “comments” has perl,VB script and C programming comment lines. The line should start with a single quote to comment in VB scripting.ĭouble slashes in the beginning of the line for single line comment in C. Then its a comment in Perl and shell scripting. If the Line starts with single hash symbol, This file shows the comment character in various programming/scripting languages The following example will remove three various kind of comment lines in a file using OR in a grep command.įirst, create a sample file called “comments”. “subexpression1|subexpression2” matches either subexpression1 or subexpression2. Pipe character (|) in grep is used to specify that either of two whole subexpressions occur in a position. In this article, let us review some advanced regular expression with examples. The result is that the regex-directed engine will return the leftmost match. The regex will try all possible permutations of the regex, in exactly the same order. Only if all possibilities have been tried and found to fail, will the regex engine continue with the second character in the text. It will try all possible permutations of the regular expression at the first character. When applying a regex to a string, the regex engine will start at the first character of the string.
You can often accomplish complex tasks with a single regular expression instead of writing several lines of codes. In our previous regular expression part 1 article, we reviewed basic reg-ex with practical examples.īut we can do much more with the regular expressions.
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