Shell Programming and Scripting

Hello all,

I am new to bash. I am trying to get a sub string of a variable in a shell script. While trying to do that I get the following error:

------------------------------------------------------------------------
OHOME: /aaa/bbb/product/eee
./t.sh: line 6: /aaa/bbb/product/eee: No such file or directory
Oracle Base:
------------------------------------------------------------------------

Here is the code:

------------------------------------------------------------------------
#!/bin/sh

OHOME=/aaa/bbb/product/eee
echo " OHOME: "$OHOME

O_BASE=echo $OHOME | awk -F"/" '{for(i=2;i<=NF;i++) {if($i=="product"){exit;} a=a"/"$i; }} '

echo " Oracle Base: "$O_BASE
------------------------------------------------------------------------

I am very surprised. Since it does not seem to like "echo $OHOME" I tried several things like enclosing in brackets, single/double quotes, etc. I still get this error. I cannot seem to find the syntax from the book or google

Looks very simple, but I am stuck on this for hours. Maybe experts here can guide me.

Here is our Linux version:

Linux <name> 2.6.9-67.0.20.ELsmp #1 SMP Wed Jun 18 12:40:47 EDT 2008 i686 i686 i386 GNU/Linux

Rocky.

Your command means OHOME=echo and while that assignment is in place, run the command $OHOME which of course is not a valid command.

To capture the output of a command, put it in backticks (ASCII 96, not regular straight quotes):

Code:

O_BASE=`echo $OHOME | awk -F"/" '{for(i=2;i<=NF;i++) {if($i=="product"){exit;} a=a"/"$i; }} '`

$OHOME should properly be in double quotes, learn that now and you will get fewer surprises later (although in this case it doesn't really make a difference).

If your shell allows $(...) instead of backticks `...` that is perhaps more readable, although nominally less portable to legacy Bourne shell.

Your awk script doesn't appear to do anything with the a part, if you mean to capture it, you need to print it.

To strip off everything after the first occurrence of /product/ you can use the shell's variable substitution mechanism:

Code:

O_BASE=${OHOME%/product/*}

(Your awk script skips the first component /aaa, is that intentional? You can remove that with another variable substitution, O_BASE=${O_BASE#/aaa})

Ahhh.. Thanks a lot. I forgot the `s when I copied it over from HP. It works with both `` and $(..)

Your second suggestion "O_BASE=${OHOME%/product/*}" works perfectly without all the extras. I cannot understand that one - need to get a good book to learn that syntax.

On the third part, the way this awk works is, it assumes the part before the first slash as a field: "/aaa/bbb/product/eee". In this one, aaa is the second field per awk and bbb is the third field.

Problem resolved. THanks a lot for your help.

Yes, because HP-UX's sh is a Posix shell. See man sh-posix to find out about its capabilities.
Therefore, you should rather use the $(...) style if you don't intend to run the script
unmodified on AIX's or SunOS/Solaris' sh.

this Reference Cards apendix from the Advanced Bash Scripting Guide (http://tldp.org/LDP/abs/html/) has been a boon to me 'cos I can never remember the correct syntax for string slicing.