Awk is printing the second line from file 1 because you have not supplied any input to the awk command. By default, with no input supplied, awk reads from stdin. The way that Ksh and bash function, anything reading from stdin within a while with redirection like this, will also read from the redirected input. So, the while loop reads the first line, and when awk is called it reads the rest, starting with line 2.
If you run this simple script, you will notice that the awk prints all lines except the first, and the while exits after running the awk only once because the end of stdin is reached:
You are seeing awk print only one line because you have added the test NR == 1; this is making the behaviour a bit more difficult to understand.
If your goal is to read each line from file 1 (the student records) and use awk to do some processing on each, maybe you should just let awk parse the file directly rather than reading each line into a shell variable and attempting to work on it with awk. It is certainly more efficient to let awk do the file i/o in this case. Here's a sample:
I made assumptions about your input data and am sorry if they aren't correct, but this should provide enough illustration to get going again.
Quote:
the "[" is a built-in for "test".
And for the record, '[' is NOT a shell built-in. It is a binary, or somtimes a sym-link to the test command, and generally 'lives' in /usr/bin. The [[ expression ]] construct in Kshell and bash is built-in. Both expression types have similar, yet very different, functionality and using test is not as efficient.
Last edited by agama; 06-25-2011 at 03:14 PM..
Reason: clarification/typo
In Korn Shell and bash, the constructs if [[ expression ]] and if (( expression )) are interpreted by the shell. The if [ expression ] is actually a command that the shell executes; the '[' is the command name.
The first noticeable difference is the overhead that the '[' command requires as a new process must be started, the binary loaded, and then cleaned up all to evaluate the expression to determine true or false. If you don't need to use the single bracket command, it is much more efficient to use the built-in evaluation.
Something that isn't obvious is that Kshell treats the right hand side of the expression as a pattern; the test (or [ command) does not. This allows you to do something like this:
Bash might do this too; I'm not a heavy bash user so I don't know for sure.
The (( expression )) is meant for numerical expressions while the double bracketed version is meant for string expressions. While this is still supported:
Kshell will give a warning (when run with -n) that it is obsolete. This would be the preferred syntax:
Hi
I have two columns and I would like to create a third column based on how many lines away from a value of 1 in column 2,
for example I have
1,0
2,0
3,0
4,0
5,0
6,1
7,0
8,0
9,0
10,0
11,1
And I want an output (6 Replies)
i have an email list in file.txt with comma separated
line1 - FIELD1,pippo@gmail.com,darth@gmail.com
line2 - FIELD2,pippo@gmail.com,darth@gmail.com,sampei@gmail.com
output=(awk -F ',' -v var="$awkvar" '$1==var {print $2,$3,$4}' spreadsheet.txt)but awk delete some letters at the... (8 Replies)
i have a datafile that has several lines that look like this:
2,dataflow,Sun Mar 17 16:50:01 2013,1363539001,2990,excelsheet,660,mortar,660,4
using the following command:
awk -F, '{$3=strftime("%a %b %d %T %Y,%s",$3)}1' OFS=, $DATAFILE | egrep -v "\-OLDISSUES," | ${AWK} "/${MONTH} ${DAY}... (7 Replies)
I thought I had solved this problem but after testing the script I came to realize that it is not doing what I need. So, here it goes again. This is the code:
awk '/\>/{F=$2; N=$3; split(FILENAME, A, "."); getline; x = ">"}{print ">" A"-" x++" "F" " N"\n" $0}'
This is the input file:
... (5 Replies)
Find the number of files with sizes > 100KB in /, /bin, /usr, /usr/bin
and /usr/sbin directories and output them in a two column format with the
name of the directory and the number of files.
i tried with awk
$>ls -lh | awk '/^-/ && $5 >= 100k {print $8 $5}'
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Hi
I have many problems with a script. I have a script that formats a text file but always prints the same error when i try to execute it
The code is that:
{
if (NF==17){
print $0
}else{
fields=NF;
all=$0;
while... (2 Replies)
Actually I got a list of file end with *.txt
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For example:
I got the file below:
file1.txt
file2.txt
file3.txt... (4 Replies)
Hi there every body
I'm new to shell scripting and there is a problem facing me,, please look at the following piece of code:
awk '
BEGIN{
FS="<assertion id=\1";
RS="<assertion id=\"2"}/<assertion id=\"1/{print FS$2 > "/home/ds2/test/output.txt"}
' filename
all I wanna do is to... (6 Replies)
Hi All,
How can i store a value of the unix command executed in AWK with system command.
devise=`cut -c1-3 dvgp.txt`
I wrote this command in awk as
awk'{
code= sprintf("devise=`cut -c1-3 dvgp.txt`");
system(code);
}'
Is this correct. can you please suggest me how the code can be... (1 Reply)
Hi,
I posted something here about this yesterday but I can't seem to
find it. I needed help writting a script which would append a file
with new lines after every so many charachters.
Example: (my original flat file)
L60 LETTER OF CREDIT 60 DAYS W00 ON RECEIPT WIRE TRANSFER W30 NET... (12 Replies)