Visit Our UNIX and Linux User Community


egrep understanding problem


 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting egrep understanding problem
# 1  
Old 01-29-2008
egrep understanding problem

Hi,
Can anyone please let me know the meaning of this line,i am not able to understand the egrep part(egrep '^[0-9]{1,2}).This will search for this combination in beginning but what does the values in {}signifies here.

/bin/echo $WhenToRun | egrep '^[0-9]{1,2}:[0-5][0-9]$' >/dev/null

Last edited by namishtiwari; 01-29-2008 at 07:38 AM..
# 2  
Old 01-29-2008
Quote:
Originally Posted by namishtiwari
Hi,
Can anyone please let me know the meaning of this line,i am not able to understand the egrep part(egrep '^[0-9]{1,2}).This will search for this combination in beginning but what does the values in {}signifies here.

/bin/echo $WhenToRun | egrep '^[0-9]{1,2}:[0-5][0-9]$' >/dev/null
Please use the man pages when you can

From man egrep.

Code:
       A  regular  expression  may  be  followed by one of several repetition
       operators:
       ?      The preceding item is optional and matched at most once.
       *      The preceding item will be matched zero or more times.
       +      The preceding item will be matched one or more times.
       {n}    The preceding item is matched exactly n times.
       {n,}   The preceding item is matched n or more times.
       {n,m}  The preceding item is matched at least n times,  but  not  more
              than m times.


Previous Thread | Next Thread
Test Your Knowledge in Computers #878
Difficulty: Medium
Memory allocation is less critical in a real-time operating system (RTOS) than in other operating systems.
True or False?

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

Egrep problem

Hi everyone, Can someone look this over? find /oracle/diag/rdbms/*/*/trace -type f -name '*d00*.trc' -mtime 0 \ -exec egrep -c 'TNS-12535: TNS:operation timed out' '{}' '+' | awk -F: '{print $1}' | egrep -c '2015-01-22' usidp/trace/abcdef_d001_21751.trc:9 \... (1 Reply)
Discussion started by: bdby
1 Replies

2. Shell Programming and Scripting

Problem with egrep and cat

Hello, I want to find some keywords in a dd image. I have created a keyword file (1.txt) and search the dd image using, cat /media/sdb1/test/c.dd.001 | strings | egrep -i --color -f 1.txt It works, But how can I get the file name and path? Many thanks. (7 Replies)
Discussion started by: yzy9951
7 Replies

3. Shell Programming and Scripting

Problem in understanding debugging

Hi i was going through the script debugging technique. below example was given in the book. 1 #!/bin/sh 2 3 Failed() { 4 if ; then 5 echo "Failed. Exiting." ; exit 1 ; 6 fi 7 echo "Done." 8 } 9 10 echo "Deleting old backups,... (11 Replies)
Discussion started by: scriptor
11 Replies

4. Shell Programming and Scripting

Problem in understanding export uses

i am beginner in shell scripting. not able to understand what below line will do. PS1=${HOST:=´uname -n´}"$ " ; export PS1 HOST below is the script #!/bin/hash PS1=${HOST:=´uname -n´}"$ " ; export PS1 HOST ; echo $PS1 and i getting the below output ´uname -n´$ (25 Replies)
Discussion started by: scriptor
25 Replies

5. UNIX for Dummies Questions & Answers

Problem understanding Paths

If I don't explain my issue well enough, I apologize ahead of time, extreme newbie here to scripting. I'm currently learning scripting from books and have moved on to the text Wicked Cool Shell Scripts by Dave Taylor, but there are still basic concepts that I'm having trouble understanding. ... (10 Replies)
Discussion started by: Chasman78
10 Replies

6. UNIX for Dummies Questions & Answers

Problem pattern redundancy with egrep

%%%%% (2 Replies)
Discussion started by: lucasvs
2 Replies

7. Shell Programming and Scripting

Formatting problem with cat, egrep and perl

Hi guys I'm using the following script to change input file format to another format. some where I'm getting the error. Could you please let me know if you find out? cat input.txt|egrep -v ‘^#'|\ perl -ane ‘if (@F>3){$_=~/(chr.+):(\d+)\ s()/;print $1,”\t”,$2,”\t”,($2+35),”\n”}'\ > output.bed ... (1 Reply)
Discussion started by: repinementer
1 Replies

8. Shell Programming and Scripting

Problem using egrep: spaces and newline

Hello: I am working in bash and am a newbie. I want to eliminate spaces from strings. Since this is a basic operation, I searched online and implemented the suggestions; however, I am facing a problem here. I have an input file which looks like this: abc defghi jklmno pqrs tuvw xyzabcd... (8 Replies)
Discussion started by: andyu11
8 Replies

9. Shell Programming and Scripting

egrep problem

Hello Experts, I am trying to parse a gz file like this gzip -cd filename | xargs egrep -h -e '.*somepattern</TAG>' | grep -c '<TAG2>`date '+%Y-%m-%d'`</TAG2>' But I am getting an error : egrep cant open. Any ideas fellas? (1 Reply)
Discussion started by: King Nothing
1 Replies

10. Shell Programming and Scripting

egrep problem | printing next line?????

Hi !!! Dear People, Please help me with the following problem. consider this output: Top 5 Timed Events ~~~~~~~~~~~~ Total Event Waits Time (s) Ela Time ---------------------------- ------------ ----------- ----- CPU time ... (3 Replies)
Discussion started by: user__user3110
3 Replies

Featured Tech Videos