behaviour of awk

Thread Tools Search this Thread
# 1  
behaviour of awk

Can someone explain how the below awk simulates cat?
pandeeswaran@ubuntu:~$ awk '1' file
PSAPSR3 3722000 91989.25 2 98
PSAPSR7 1562000 77000.1875 5 95
PSAPUNDO 92000 4087.5625 4 96
pandeeswaran@ubuntu:~$ awk '2' file
PSAPSR3 3722000 91989.25 2 98
PSAPSR7 1562000 77000.1875 5 95
PSAPUNDO 92000 4087.5625 4 96
pandeeswaran@ubuntu:~$ awk '0' file
pandeeswaran@ubuntu:~$ awk '3' file
PSAPSR3 3722000 91989.25 2 98
PSAPSR7 1562000 77000.1875 5 95
PSAPUNDO 92000 4087.5625 4 96

So, any non zero value covered by '' will give the result similar to cat?
How it works?
# 2  
Refer to the awk man page:

       A pattern-action statement has the form

              pattern { action }

       A missing { action } means print the line; a missing pattern always matches.  Pattern-action  statements
       are separated by newlines or semicolons.

"1" is the pattern which evaluates to true. As no "action" is specified, the line is printed.

It's equivalent to:
1 == 1 { print }

1 { print }

or just
{ print }

This User Gave Thanks to Scott For This Post:
# 3  
Thanks scott..but i am curious why the below is not working?
awk '-1==-1' file

# 4  
That's an interesting question!

awk seems to treat the first - as an option. Using awk ' -1 == -1^ (see the space before the first -), or awk -- '-1 == -1^ gets around that.

Previous Thread | Next Thread
Thread Tools Search this Thread
Search this Thread:
Advanced Search

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

awk Strange behaviour in AIX

Can someone please explain the strange behaviour.. I was just trying a few things to learn awk.. in the below code when I start the braces in the same line, the output is as expected, when I start at next line, output is displayed twice. Please see the file, code I tried and output below. ... (2 Replies)
Discussion started by: Kulasekar
2 Replies

2. Shell Programming and Scripting

Strange behaviour of arrays in awk

Imagine 2 files f1 f2: file1_l1_c1 code_to_find file1_l1_c3 file1_l2_c1 file1_code2 file1_l2_c3 file1_l3_c1 file1_code3 file1_l3_c3 file2_l1_c1 file2_l1_c2 code_to_find file2_l2_c1 file2_l2_c2 file2_code5 file2_l3_c1 file2_l3_c2 file2_code3 Say we want to print lines from f2 having... (5 Replies)
Discussion started by: ripat
5 Replies

3. UNIX for Dummies Questions & Answers

Strange behaviour when output to terminal vs file (awk)

Hi all ! I noticed something very weird. I have a large pipe delimited file (20 fields/3,000 records) that looks like that: AAA|BBB|11111|22222|...|($NF of record 1) CCC|DDD|33333|44444|...|($NF of record 2) CCC|DDD|55555|66666|...|($NF of record 3) For the lines with same 1st and 2nd... (3 Replies)
Discussion started by: beca123456
3 Replies

4. Programming

different behaviour in fg and bg

fg = foreground bg = background I have a cobol program that I start with a very simple script. The script is not at fault as it has not changed and the program worked in fg and bg before. I have altered the logging in the program and moved my cursor declare to working storage. The program runs... (6 Replies)
Discussion started by: Bruble
6 Replies

5. Shell Programming and Scripting

Don't understand AWK asort behaviour

Hello, I have the following script : BEGIN { print "1 ***"; split("abc",T,""); T="e"; T="z"; T="y"; for (i in T) printf("%i:%s ",i,T); print ""; for (i=1; i<=length(T); i++) printf(T); print "" print "2 ***"; asort(T,U); for (i in U) printf("%i:%s ",i,U); ... (3 Replies)
Discussion started by: jgilot
3 Replies

6. UNIX for Advanced & Expert Users

eval behaviour

Hi, I have snippet like the following x="1" prompt1="hi" if I say eval echo \$prompt$x then it is giving o/p "hi" if I say `eval echo \$prompt$x` here it is giving 1 ! if I add one more escape character i.e. `eval echo \\$prompt$x` then it is giving "hi" Can you please... (3 Replies)
Discussion started by: shahnazurs
3 Replies

7. Shell Programming and Scripting

cp -R behaviour

i 've noticed the following difference between freebsd cp and gnu cp from the freebsd cp man page: -R ... If the source_file ends in a /, the contents of the directory are copied rather than the directory itself. ... on gnu cp from the man pagewhile on gnu cp manpage: -r... (2 Replies)
Discussion started by: aegis
2 Replies

8. Shell Programming and Scripting

Why this behaviour of IF condition?

I have a variable, defndata, which is a number (fetched from a file using awk). I want that if defndata is not initialized (that is its not found in the file using awk), then to execute a block of statements, otherwise execute another block. if then .... else ... fi Now this... (4 Replies)
Discussion started by: indianjassi
4 Replies

9. Shell Programming and Scripting

A Strange Behaviour!!!

Can some-one give me a view to this : I have a directory in an unix server, having permissions r-xr-xr-x .This directory is basically a source directory. Now there is another directory basically the destination directory which has all the permissions. Note:I log in as not the owner,but user... (5 Replies)
Discussion started by: navojit dutta
5 Replies

10. Programming

Can some 1 explain why this behaviour

#include <iostream> using namespace std; int main() { const int l_test = 999999999; int *l_ptr = (int*) &l_test; cout<<"Constant Addr:"<<&l_test<<" Value:"<<l_test<<endl; cout<<"Pointer Addr:"<<l_ptr<<" Value:"<<*l_ptr<<endl; *l_ptr = 888888888; // Manipulating... (2 Replies)
Discussion started by: helpmenow
2 Replies

Featured Tech Videos