extract a string within a string using a pattern

Shell Programming and Scripting
1

hi all,

i have a file name using the following pattern:

PREFIX: AR
SOURCE: LEGACY
DATETIME: YYYYMMDD_HH24MISS
SUFFIX: .txt

sample filename:

AR_LEGACY_20101104_105500.txt

i want to extract the source which is LEGACY in this case. how do i do this using shell?

thanks.

2

You didn't mention what shell. If you use the external sed command this should work for most:

SOURCE=`echo $file | sed "s/^AR_//;s/_.*//"`

For bash/ksh

SOURCE=${file#AR_}
SOURCE=${SOURCE%%_*}
3

thanks. how can i get the shell ? i'm using Linux.

[ ~]$ uname
Linux

how can i do this in sed even if prefix is other than AR? i tried the following but doesnt work.

[ ~]$ source=`echo $file | sed "s/^*_//;s/_.*//"`
[ ~]$ echo $source
AR
[ ~]$ source=`echo $file | sed "s/*_//;s/_.*//"`
[ ~]$ echo $source
AR

thanks.. actually the prefix can be other than AR. so i tried

file=AR_LEGACY_20101104_105500.txt
source=${file#*_}
source=${source%%_*}
echo $source

seems to work.

4

To determine shell:

$ ps -p$$

If other than AR_ this should work too:

SOURCE=`echo $file | sed "s/^[^_]*_//;s/_.*//"`
5

[~]$ ps -p$$
PID TTY TIME CMD
20855 pts/5 00:00:00 bash
[~]$

thanks