hello i have the following awk script:
#!/bin/awk -f
{for(i=4;i<=7;i++) j+=$i; print "Student",NR",",$1,$2",",j/4; j=0}
and i want to append the output to a new file (newfile.txt).
Could you please try following. Where mention output file inside awk code itself.
{for(i=4;i<=7;i++) j+=$i; print "Student" OFS NR",",$1,$2"," OFS j/4 >> (output_file); j=0}
OR 2nd way is when you are running your awk code where script is the script name you are calling to run your awk program eg-->
./script >> output_file
In case you want to run an awk one-liner to get output into a output file then try following.
awk -v output_file="Output.txt" '{for(i=4;i<=7;i++) j+=$i; print "Student" OFS NR",",$1,$2"," OFS j/4 >> (output_file); j=0}' Input_file
In above code I have created a variable named output_file whose value you could keep it as per your wish too.
Don't use a shebang to call awk from a shell script as it robs you of the ability to separate your functionality by what each (the shell or awk) does best. Make your shell script look like this instead (using whichever shell you use for the shebang):
#!/bin/env bash
awk '
{for(i=4;i<=7;i++) j+=$i; print "Student",NR",",$1,$2",",j/4; j=0}
' "$#" >> newfile.txt
Related
I'm curious about how to set command-line options in awk script, like -F for field separator. I try to write the shebang line like
#!/usr/bin/awk -F ":" -f
and get the following error:
awk: 1: unexpected character '.'
For this example, I can do with
BEGIN {FS=":"}
but I still want to know a way to set all those options. Thanks in advance.
EDIT:
let's use another example that should be easy to test.
inputfile:
1
2
3
4
test.awk:
#!/usr/bin/awk -d -f
{num += $1}
END { print num}
run
/usr/bin/awk -d -f test.awk inputfile
will get 10 and generate a file called awkvars.out with some awk global variables in it.
but
./test.awk inputfile
will get
awk: cmd. line:1: ./test.awk
awk: cmd. line:1: ^ syntax error
awk: cmd. line:1: ./test.awk
awk: cmd. line:1: ^ unterminated regexp
if I remove '-d' from shebang line,
./test.awk inputfile
will normally output 10.
My question is that whether there is a way to write "-d" in test.awk file to generate awkvars.out file?
Answering for the OP question, beyond the setting of FS.
Short Answer: you can not use multiple options with '#!', and since you need to tell awk to read the program from stdin (-f-), you are out of luck.
Long Answer:
When using shebang (#!), there is a limit of single argument (which is passed to the named programs as the 1st argument. So in general:
#! /path/to/prog arg1
input-1
input-2
Will execute /path/to/prog arg1, with the content of the file (including the leading shebang) available as stdin. This is oversimplification, actual rules are more complex., see https://unix.stackexchange.com/questions/87560/does-the-shebang-determine-the-shell-which-runs-the-script
Given this limitation of one argument, when executing awk, the only valid and required parameter is '-f', which indicates that the awk programs is provided on STDIN. You can prepend few other options that do NOT take any argument, for example 'traditional' (e.g., '-Pf-' will force POSIX behavior).
As much as I can tell, all the 'interesting' options (setting FS, RS, ORS, ...) need to be separated from the '-f-' with a space, making it impossible to embed them into the command line, other then using the 'BEGIN { ... }' or similar in the script.
Bottom line, trying #! /usr/bin/awk -f- -F, will attempt to look for program is the same as awk -f' -F', and will look for a file named '- -F`. Usually not very useful, and will not set the FS.
Let's say following is our Input_file, which we are going to use for all mentioned solutions here.
cat Input_file
a,b,c,d
ab,c
1st way of setting Field separator: 1st simple way will be setting FS value in BEGIN section of awk program file. Following is our .awk file.
cat file1.awk
BEGIN{
FS=","
}
{
print $1"..."$2
}
Now when we run the code following output will come:
/usr/local/bin/awk -f file1.awk Input_file
a...b
ab...c
2nd way of setting field separator: 2nd way will be pass FS value before reading Input_file like as follows.
/usr/local/bin/awk -f file.awk FS="," Input_file
Example: Now following is the file.awk file which has awk code.
cat file.awk
{
print $1".."$2
}
Now when we run awk file with awk -f .. command as follows will be result.
/usr/local/bin/awk -f file.awk FS="," Input_file
a..b
ab..c
Which means it is picking up the field separator as , in this above program.
3rd way of setting field separator: We can set field separator in awk -f programs like how we do for usual awk programs using -F',' option as follows.
/usr/local/bin/awk -F',' -f file.awk Input_file
a..b
ab..c
4th way of setting field separator: We could mention field separator as a variable by using -v option on command line while running file.awk script as follows.
/usr/local/bin/awk -v FS=',' -f file.awk Input_file
Never use a shebang to call awk as it robs you of the ability to separate shell arguments into awk arguments and awk variables and do anything else that's better done in shell (e.g. arg parsing with getopts) before calling awk. Just call awk from inside your shell script.
Also, don't name your shell script test.awk as it's a shell script. The fact it's implemented in awk is irrelevant. There's no reason to create a file that you sometimes call as awk file to have awk interpret and other times as just file to have the shell interpret.
I'm having trouble finding out how to read in my file into my awk script.
This is what I have so far. Basically, I want to print out the header, and then read in the roster file which then I will edit to the necessary format. However, my problem is just figuring out how to read in the file.
#!/bin/awk -f
BEGIN {print "Last Name:First Name:Student ID:School – Major:Academic Level:ASURITE:Email" "\n" } {print $1,$2} roster
On running this
awk -f script.awk
Last Name:First Name:Student ID:School – Major:Academic Level:ASURITE:Email
^C
This is what I end up with - the file doesn't read in and I have to CTRL-C my way out since it doesn't close.
The idea is right, but the place where you have mentioned the input file roster is wrong. Move it out of the script. You need to understand that awk syntax is always as below
awk <action> <file>
The <action> part could be directly given in the command line or provided from a script using the -f flag. But the <file> argument still needs to be given no-matter which way. Moving it inside the script, makes awk wait for an input to read its standard input but it doesn't get any.
awk -f script.awk roster
You could modify the script.awk to just use awk without -f and use the /usr/bin/env for the shell to get the location of awk to execute
#!/usr/bin/env awk
BEGIN {
print "Last Name:First Name:Student ID:School – Major:Academic Level:ASURITE:Email" "\n"
}
{
print $1,$2
}
How to split file via awk command and customize the name of the output file?
I have tried,
awk -v RS=$val '{ outfile = "'$filename'""." NR "'.${extension}'"; print > outfile}' $file
You can use sprintf to create the filenames as
outputfile = sprintf ("filename%03d.txt", NR);
Some things to be noted in your script,
You cannot access shell variables directly in your awk script, you need to create awk variables using -v formate.
So the script should be like
awk -v filename=$filename -v extension=$extension '{ outputfile = sprintf (filename"%03d"extension, NR); print > outputfile }'
awk doesn't have any specific concatenation operator, just writing 2 strings together concatenates them.
I'd like to execute the following awk script (which is working well) in tcl:
exec awk {$1=="text" {print $0}} temp1.txt > temp2.txt}
BUT the problem is that "text" is comming from TK entry widget and I have to put it in a variable ($var) which is not recognized by awk:
set var [.entry get]
exec awk {$1==$var {print $0}} temp1.txt > temp2.txt}
Any idea how to skip it or make it running?
PS I'd like to stay with awk, not to change the code on tcl if it's possible.
Regards,
lucas
Use -v switch in awk to pass external variable to awk:
exec awk -v var=$var {$1==var {print $0}} temp1.txt > temp2.txt}
I am using the below code to change an existing awk script so that I can add more and more cases with a simple command.
echo `awk '{if(/#append1/){print "pref'"$1"'=0\n" $0 "\n"} else{print $0 "\n"}}' tf.a
note that the first print is "pref'"$1"'=0\n" so it is referring to the variable $1 in its environment, not in awk itself.
The command ./tfb.a "c" should change the code from:
BEGIN{
#append1
}
...
to:
BEGIN{
prefc=0
#append1
}
...
However, it gives me everything on one line.
Does anyone know why this is?
If you take awk right out of the equation you can see what's going on:
# Use a small test file instead of an awk script
$ cat xxx
hello
there
$ echo `cat xxx`
hello there
$ echo "`cat xxx`"
hello
there
$ echo "$(cat xxx)"
hello
there
$
The backtick operator expands the output into shell "words" too soon. You could play around with the $IFS variable in the shell (yikes), or you could just use double-quotes.
If you're running a modern sh (e.g. ksh or bash, not the "classic" Bourne sh), you may also want to use the $() syntax (it's easier to find the matching start/end delimiter).
do it like this. pass the variable from shell to awk properly using -v
#!/bin/bash
toinsert="$1"
awk -v toinsert=$toinsert '
/#append1/{
$0="pref"toinsert"=0\n"$0
}
{print}
' file > temp
mv temp file
output
$ cat file
BEGIN{
#append1
}
$ ./shell.sh c
BEGIN{
prefc=0
#append1
}