Reading a file from a specified offset

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# 1  
Old 12-12-2007
Reading a file from a specified offset


I want to read a file from a specified offset from the start of file. With the read command, is it possible to do so. Please suggest. Is there any other alternative?

# 2  
Old 12-12-2007
Do you mean the system call read()? If so use lseek() beforehand to seek into the file to the offset you want.
# 3  
Old 12-13-2007
Thanks Porter. I have calculated the offset from where I have to read. I believe before using lseek, I will have to open the file using open system call. I am getting a syntax error when I try to open the file. Please see code below:

apdma001:/amex/home/mqm/.saurabh # vi Myprog
"Myprog" 30 lines, 924 characters
# This is my first program

USAGE="Myprog <profile to be searched> "
if [ $# -ne 1 ]
echo "Invalid number of arguements :USAGE : $USAGE "

# Write all relevant profiles into Myprog1. Filter those lines which have "MQQUEUE" so that only one occurance is listed

grep $strToSearch Sarah.txt | grep -v MQQUEUE > Myprog1
echo "Following profiles have been found:"

while [ 1 ]
read myline || break
# Remove "(G)" from the profile name
set -A profileNm $myline
# Search for second occurance of profileNm and read the line number of the second occurance
grep -n $profileNm Sarah.txt | head -n 2 | tail -n 1 | cut -f1 -d ":" | read startline
# Increase offset by 57 to move to access area
startline=`expr $startline + 57`
echo "$profileNm : $startline"
done < $myfile

Myprog[18]: 0403-057 Syntax error at line 18 : `(' is not expected.
I am new to unix, so my questions may appear very silly. But I am just trying to learn. Appreciate your help.

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