07-14-2010
It simply uses extended regular expressions by default instead of basic regular expressions. You can do the same with 'grep -E'.
In extended regular expressions, parenthesis are metacharactes which are used for grouping and capturing; thus, they must be escaped if they are to be matched literally. In basic regular expressions, the parenthesis are not metacharacters and must be quoted if they are to be used to capture or group.
Although egrep defaults to using a more powerful regular expression language, the command itself is not in any way more robust ... imo.
Regards,
Alister
10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
Hi,
The input file "notifications" contains the following string.
FRTP has 149 missing batches
I want to search for :
FRTP has missing batches
As the number 149 is not important and will change.
The commands I have tried.
grep "FRTP has.*missing batches" notifications.txt... (3 Replies)
Discussion started by: whugo
3 Replies
2. Shell Programming and Scripting
hi ,
I'm new at unix bash scripting, im playing a little bit with egrep/grep.
I have serveral files and i do a search on those files, like "aki", the result
is many rows outcoming and serveral of them are dubble because aki wil come more than ones in a file, how can i get a result that it... (3 Replies)
Discussion started by: tvrman
3 Replies
3. Shell Programming and Scripting
Hi
I use arp to get the mac-addresses of my hosts.
# arp -a | grep 192.168.0.
e1000g0 192.168.0.1 255.255.255.255 o 00:00:00:00:00:01
e1000g0 192.168.0.11 255.255.255.255 o 00:00:00:00:00:02
e1000g0 192.168.0.2 255.255.255.255 ... (12 Replies)
Discussion started by: domi55
12 Replies
4. Shell Programming and Scripting
Is it possible to use the escape sequence:
\r
to match a line feed in grep/egrep?
I want to use a regexp that crosses over two lines, and it does not seem to be possible. (1 Reply)
Discussion started by: Enobarbus37
1 Replies
5. UNIX Desktop Questions & Answers
Hi All,
Can anyone please explain me the difference between grep, egrep and fgrep with examples.
I am new to unix environment.. Your help is highly appreciated.
Regards,
ravi (2 Replies)
Discussion started by: ravind27
2 Replies
6. UNIX for Dummies Questions & Answers
Hi All,
Please i need to know the difference between grep, egrep & grep -i when used to serach through a file.
My platform is SunOS 5.9 & i'm using the korn shell.
Regards,
- divroro12 - (2 Replies)
Discussion started by: divroro12
2 Replies
7. Shell Programming and Scripting
Dear Friends,
I have a command which can result following output.
Packet is: /var/adm/yyyy/pkt6043
Intended for network : /vob/repo
I would like to retrive
pkt6043 and /vob/repo using single command.
Blue color test will be always contstant and red color text will be dynamic
... (2 Replies)
Discussion started by: baluchen
2 Replies
8. Shell Programming and Scripting
All,
I have a problem with grep/fgrep/egrep. Basically I am building a 200 times 200 correlation matrix. The entries of this matrix need to be retrieved from another very large matrix (~100G). I tried to use the grep/fgrep/egrep to locate each entry and put them into one file. It looks very... (1 Reply)
Discussion started by: realwindfly
1 Replies
9. Homework & Coursework Questions
Use and complete the template provided. The entire template must be completed. If you don't, your post may be deleted!
1. The problem statement, all variables and given/known data:
I have a text file.
1) How do I search for x and y?
'Find all lines that contain David and Emily'
2) How do I... (1 Reply)
Discussion started by: ninjagod123
1 Replies
10. Shell Programming and Scripting
The $ seems to fail for me. I'm using GNU grep 2.5.4 (that is, nothing out of the ordinary, just what came with my distro) but I can't get the final anchor $ to work for me. (^ works as usual.)
Behavior without anchor:
$ /bin/grep -E 'tium' file
tritium
tertium quid
Expected behavior:
$... (2 Replies)
Discussion started by: CRGreathouse
2 Replies
GREP(1) General Commands Manual GREP(1)
NAME
grep, egrep, fgrep - search a file for a pattern
SYNOPSIS
grep [ option ] ... expression [ file ] ...
egrep [ option ] ... [ expression ] [ file ] ...
fgrep [ option ] ... [ strings ] [ file ]
DESCRIPTION
Commands of the grep family search the input files (standard input default) for lines matching a pattern. Normally, each line found is
copied to the standard output. Grep patterns are limited regular expressions in the style of ex(1); it uses a compact nondeterministic
algorithm. Egrep patterns are full regular expressions; it uses a fast deterministic algorithm that sometimes needs exponential space.
Fgrep patterns are fixed strings; it is fast and compact. The following options are recognized.
-v All lines but those matching are printed.
-x (Exact) only lines matched in their entirety are printed (fgrep only).
-c Only a count of matching lines is printed.
-l The names of files with matching lines are listed (once) separated by newlines.
-n Each line is preceded by its relative line number in the file.
-b Each line is preceded by the block number on which it was found. This is sometimes useful in locating disk block numbers by con-
text.
-i The case of letters is ignored in making comparisons -- that is, upper and lower case are considered identical. This applies to
grep and fgrep only.
-s Silent mode. Nothing is printed (except error messages). This is useful for checking the error status.
-w The expression is searched for as a word (as if surrounded by `<' and `>', see ex(1).) (grep only)
-e expression
Same as a simple expression argument, but useful when the expression begins with a -.
-f file
The regular expression (egrep) or string list (fgrep) is taken from the file.
In all cases the file name is shown if there is more than one input file. Care should be taken when using the characters $ * [ ^ | ( ) and
in the expression as they are also meaningful to the Shell. It is safest to enclose the entire expression argument in single quotes ' '.
Fgrep searches for lines that contain one of the (newline-separated) strings.
Egrep accepts extended regular expressions. In the following description `character' excludes newline:
A followed by a single character other than newline matches that character.
The character ^ matches the beginning of a line.
The character $ matches the end of a line.
A . (period) matches any character.
A single character not otherwise endowed with special meaning matches that character.
A string enclosed in brackets [] matches any single character from the string. Ranges of ASCII character codes may be abbreviated
as in `a-z0-9'. A ] may occur only as the first character of the string. A literal - must be placed where it can't be mistaken as
a range indicator.
A regular expression followed by an * (asterisk) matches a sequence of 0 or more matches of the regular expression. A regular
expression followed by a + (plus) matches a sequence of 1 or more matches of the regular expression. A regular expression followed
by a ? (question mark) matches a sequence of 0 or 1 matches of the regular expression.
Two regular expressions concatenated match a match of the first followed by a match of the second.
Two regular expressions separated by | or newline match either a match for the first or a match for the second.
A regular expression enclosed in parentheses matches a match for the regular expression.
The order of precedence of operators at the same parenthesis level is [] then *+? then concatenation then | and newline.
Ideally there should be only one grep, but we don't know a single algorithm that spans a wide enough range of space-time tradeoffs.
SEE ALSO
ex(1), sed(1), sh(1)
DIAGNOSTICS
Exit status is 0 if any matches are found, 1 if none, 2 for syntax errors or inaccessible files.
BUGS
Lines are limited to 256 characters; longer lines are truncated.
4th Berkeley Distribution April 29, 1985 GREP(1)