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Substring using cut/awk/sed

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Top Forums Shell Programming and Scripting Substring using cut/awk/sed
# 15  
Old 09-24-2010
Hi ,

I have been trying various combinations of . & * but I have not yet completely understood how the placement of "." affects the o/p & can't use the [tag] sed [/tag] for this purpose very convincingly. following are some examples :

Code:
echo MPMTR20100706043000.txt|sed -n -e 's/\(..\)\(...\)\([0-9]\{8\}\)/\2,\1,\3,&/p'
MTR,MP,20100706,MPMTR20100706043000.txt

echo MPMTR20100701043000.txt|sed -n -e 's/\(..\)\(...\)\([0-9]\{8\}\)/\1,\2,\3,&/p'
MP,MTR,20100701,MPMTR20100701043000.txt

echo MPMTR20100706043000.txt|sed -n -e 's/\(..\)\(..\)\([0-9]\{8\}\)/\1,\2,\3,&/p'
MPM,TR,20100706,PMTR20100706043000.txt

echo MPMTR20100706043000.txt|sed -n -e 's/\(..\)\(.\)\([0-9]\{8\}\)/\1,\2,\3,&/p'
MPMT,R,20100706,MTR20100706043000.txt

echo MPMTR20100706043000.txt|sed -n -e 's/\(.\)\(..\)\([0-9]\{8\}\)/\1,\2,\3,&/p'
MPM,TR,20100706,MTR20100706043000.txt

echo MPMTR20100706043000.txt|sed -n -e 's/\(\)\(.\)\([0-9]\{8\}\)/\1,\2,\3,&/p'
MPMT,R,20100706,R20100706043000.txt

echo MPMTR20100706043000.txt|sed -n -e 's/\(\)\(\)\([0-9]\{8\}\)/\1,\2,\3,&/p'
MPMTR,,20100706,20100706043000.txt

can anyone please explain why the filename is getting clipped from left & why first field is not of 2 characters ?

Thanks!
# 16  
Old 09-24-2010
Sorry, but I didn't understand your problem! In which of the statements above is your problem?
# 17  
Old 09-27-2010
sorry for the late response .

Please ignore the first two o/p s .

1. In the 3rd o/p , even though I have selected first two matching occurrances it is selecting 3 characters

2. If I reduce one more dot for second string it selects 4 character for 1st field & equal number of characters get clipped from the filename in o/p.

can you explain how this happens ?

Thanks ,
sumoka.
# 18  
Old 10-20-2010
you can use cut,
Code:
main=`echo "ABCDEFGHIJ20100909.txt"`
first=`echo $main | cut -c1-2`
second=`echo $main | cut -c3-5`
third=`echo $main | cut -c11-18`
echo "$first,$second,$third,$main"

Best Luck.
# 19  
Old 10-20-2010
Quote:
Originally Posted by sumoka
sorry for the late response .

Please ignore the first two o/p s .

1. In the 3rd o/p , even though I have selected first two matching occurrances it is selecting 3 characters

2. If I reduce one more dot for second string it selects 4 character for 1st field & equal number of characters get clipped from the filename in o/p.

can you explain how this happens ?

Thanks ,
sumoka.
In the third example this is because the first character is not part of the search and replace operation (and likewise aren't the last 10 characters). Look what happens when we do this:
Code:
$ echo MPMTR20100706043000.txt|sed -n -e 's/\(..\)\(..\)\([0-9]\{8\}\)//p'
M043000.txt

Code:
$ echo MPMTR20100706043000.txt|sed -n -e 's/\(..\)\(..\)\([0-9]\{8\}\).*//p'
M

Code:
$ echo MPMTR20100706043000.txt|sed -n -e 's/.\(..\)\(..\)\([0-9]\{8\}\).*//p'

Code:
$ echo MPMTR20100706043000.txt|sed -n -e 's/.\(..\)\(..\)\([0-9]\{8\}\).*/\1,\2,\3,&/p'
PM,TR,20100706,MPMTR20100706043000.txt

# 20  
Old 10-20-2010
Quote:
Originally Posted by sumoka
sorry for the late response .

Please ignore the first two o/p s .

1. In the 3rd o/p , even though I have selected first two matching occurrances it is selecting 3 characters

2. If I reduce one more dot for second string it selects 4 character for 1st field & equal number of characters get clipped from the filename in o/p.

can you explain how this happens ?

Thanks ,
sumoka.
Because your coding has contains some mistakes..

Code:
echo MPMTR20100706043000.txt|sed -n -e 's/\(..\)\(..\)\([0-9]\{8\}\)/\1,\2,\3,&/p'
MPM,TR,20100706,PMTR20100706043000.txt

your string is "two chars + two chars + 8 numbers"
but after the second "two chars" there is a char before the 8 numbers

so your code is must be is below

Code:
# echo MPMTR20100706043000.txt|sed -n -e 's/\(..\)\(..\).\([0-9]\{8\}\)/\1,\2,\3,&/p'
MP,MT,20100706,MPMTR20100706043000.txt

# 21  
Old 10-20-2010
sed will try to match the biggest pattern possible

Code:
# echo MPMTR20100706043000.txt|sed -n -e 's/\([0-9][0-9]\).*\([0-9][0-9]\)/\1,\2,&/p'
MPMTR20,00,20100706043000.txt
# echo MPMTR20100706043000.txt|sed -n -e 's/\([0-9][0-9]\).*\([0-9][0-9]\)/\1,\2,&/gp'
MPMTR20,00,20100706043000.txt
# echo MPMTR20100706043000.txt|sed -n -e 's/\([0-9][0-9]\).*\([0-9][0-9]\)/\1,\2,&/1p'
MPMTR20,00,20100706043000.txt
#

and the & will be what is matched between the / / but it looks like a right expansion is performed since the .txt still remains

Note : The following will match nothing whereas we could have thought of a reverse search for the pattern like :
20100706043000
2010070604300
201007060430
20100706043
2010070604
...
see :
Code:
# echo MPMTR20100706043000.txt|sed -n -e 's/\([0-9][0-9]\).*\([0-9][0-9]\)/\1,\2,&/2p'
# echo MPMTR20100706043000.txt|sed -n -e 's/\([0-9][0-9]\).*\([0-9][0-9]\)/\1,\2,&/3p'
#

Note : that the \1 and \2 have their left and right expansion automatically performed even if not explicitly specified in the \( ...\) matching : look
Code:
# echo MPMTR20100706043000.txt|sed -n -e 's/\([0-9][0-9]\).*\(3[0-9][0-9]\)/\1,\2,&/p'
MPMTR20,300,20100706043000.txt

Last edited by ctsgnb; 10-20-2010 at 05:45 AM..
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