how to extract a value from a inputfile in script

[Frank Zeng]

Hi,
I want to extract a value from a input file so
that I can use it to determine the iteration in
the c shell script file.

Thanks

[boley janowski]

set the value in the input file as a variable, or set the script to cat the file and look for something specific and set that output as a variable:

x=`cat file | grep | awk '{print $}`

with this defined in the shell script. If this is not what your looking for, please provide and example.

[James R. Ferguson]

Hi Frank:

You can use 'awk' to read a particular file, selecting record(s) and extracting fields, as for instance:

# X=`awk '$2~/localhost/ {print $1}' /etc/hosts`

# echo $X

...which would display 127.0.0.1

You can also use the 'read' command to split a line read from a file into individual fields. Take a look at 'man read'.

...JRF...

[Frank Zeng]

I tried the codes you provided, but they seemed they didn't work. I don't know if I did
something wrong. I also tried "read", it didn't work either. What I did is as following,

while (read -r xx yy)
do
printf "%s %s\n" "$yy" "$xx"
done < filein.dat


and the inputfile "filein.dat" is as following

12. 12.
11. 11.

[James R. Ferguson]

Hi Frank:

Both the 'awk' and the 'read' will work in c-shell. Remove the parentheses surrounding the read argument to make it work:

...
while read -r xx yy
...

...JRF...

[Frank Zeng]

Hi, James,

I did what you said. What I got is as the following,

while: Expression syntax

Thanks

[James R. Ferguson]

Hi Frank:

My apologies! I tested the syntax but bungled specifying the C-shell!

I never use the C-shell. It's not nearly as robust as the Posix (superset of ksh) that is the HP default. The syntax I used is Posix.

For the C-shell you would do:

# set X=`awk '$2~/localhost/ {print $1}' /etc/hosts`

...JRF...

[Wodisch]

Hello Frank,

guessing that your "config file" looks like:
NAME=value

you could use a line like:

result=`grep "NAME=" config-file | cut -d"=" -f2-`

that should be pretty "shell-independent" and fast
enough.

HTH,
Wodisch

[Jordan Bean]

The CSH doesn't have a built-in "read" function. Instead, it will use /usr/bin/read, a shell script which invokes the posix shell to use its builtin-in read. This is actually pretty useless since the information is lost when the script terminates. I recommend using the posix shell as much as possible.

If you want to read in a CSV file using the posix shell, try:

IFS=","
while read xx yy
do
echo $yy $xx
done <<.
12,13,
14,15,
.

I don't know of any equivalent for CSH.

[Frank Zeng]

Hello, James,

The follwing works, but I still don't how to read the value from the file "filein.dat"
could you tell me explicitly.

Thanks.

set X=`awk '$2~/localhost/{print$1}' /etc/hosts`
echo $X

[Jordan Bean]

Frank, could you tell us exactly what you are trying to do? What is the nature of the input file? Which value do you want? How will it be used? Perhaps we can engineer a efficient solution for you with more details.