Top Forums Shell Programming and Scripting awk one liners into a nice script Post 302852721 by Jotne on Thursday 12th of September 2013 09:26:25 AM
Old 09-12-2013
As long as we do not have input data and desired output data, its difficult to shorten them.
 

7 More Discussions You Might Find Interesting

1. Programming

nice command and nice() system call

Hi I want to implement the nice command in the shell that I am building. I came to know that there is a corresponding nice() system call for the same. But since I will be forking different processes to run different commands typed on the command prompt, is there any way I can make a command... (2 Replies)
Discussion started by: tejbuch
2 Replies

2. UNIX for Dummies Questions & Answers

How to Turn perl one-liners into full perl script?

I have the following command prompt perl one liner: perl -e 's/\(\)\\,\"]//g; s/^\s//g; s/;/\n/g' -pi result1 I tried to move this one liner into a perl script I am practicing with (just started learning perl right now). I tried the following (I only know how to open a file and output to a... (1 Reply)
Discussion started by: EDALBNUG
1 Replies

3. Red Hat

KSH script help needed ( nice error trap routine ?)

I am running a script that runs a loop and executes a command on ${i} until the end of the for loop. From time to time the command generates an error ( which is good) for example ERROR0005: How can I trap the error and send an email echoing the ${i} variable in the loop and the error ? ... (2 Replies)
Discussion started by: pcpinkerton
2 Replies

4. Shell Programming and Scripting

awk - one liners

Guys, I have a requirement like this. A file has >5K records always. Separated by "|", it has 30 fields for each line. In some lines, I am getting an odd field. say, the 15th field is supposed to be 2 characters but comes in as >2. In this case, for resolving this I need to copy the value of... (6 Replies)
Discussion started by: PikK45
6 Replies

5. Shell Programming and Scripting

Set nice value in an executable in a script?

Is it possible to set a nice value for an executable in a script so that every time the executable runs it has this nice value? I'm trying to set aerender (After Effects terminal renderer) to run at +18 by replacing the original aerender script with a bash script with something like this in it: ... (3 Replies)
Discussion started by: scribling
3 Replies

6. What is on Your Mind?

Those simple one liners

I wanted to say LOL and punch my face when I saw post#11 (where Don_Cragun even reduced the string manipulation with a simple regex) in the thread https://www.unix.com/shell-programming-scripting/220553-add-0-start-filename-2.html I mean, when things can be done with just a one liner, sometimes I... (6 Replies)
Discussion started by: ahamed101
6 Replies

7. AIX

Useful and nice script for AIX,but outdated

How can I quickly see disk usage for my entire system? - IBM: AIX FAQ - Tek-Tips I tried it on aix7.1with ./script -dand give me VG PV size used free location Description rootvg 128 397 149 rootvg 128 212 334 ... (1 Reply)
Discussion started by: Linusolaradm1
1 Replies
A2P(1)							 Perl Programmers Reference Guide						    A2P(1)

NAME
a2p - Awk to Perl translator SYNOPSIS
a2p [options] [filename] DESCRIPTION
A2p takes an awk script specified on the command line (or from standard input) and produces a comparable perl script on the standard output. OPTIONS Options include: -D<number> sets debugging flags. -F<character> tells a2p that this awk script is always invoked with this -F switch. -n<fieldlist> specifies the names of the input fields if input does not have to be split into an array. If you were translating an awk script that processes the password file, you might say: a2p -7 -nlogin.password.uid.gid.gcos.shell.home Any delimiter can be used to separate the field names. -<number> causes a2p to assume that input will always have that many fields. -o tells a2p to use old awk behavior. The only current differences are: o Old awk always has a line loop, even if there are no line actions, whereas new awk does not. o In old awk, sprintf is extremely greedy about its arguments. For example, given the statement print sprintf(some_args), extra_args; old awk considers extra_args to be arguments to "sprintf"; new awk considers them arguments to "print". "Considerations" A2p cannot do as good a job translating as a human would, but it usually does pretty well. There are some areas where you may want to examine the perl script produced and tweak it some. Here are some of them, in no particular order. There is an awk idiom of putting int() around a string expression to force numeric interpretation, even though the argument is always integer anyway. This is generally unneeded in perl, but a2p can't tell if the argument is always going to be integer, so it leaves it in. You may wish to remove it. Perl differentiates numeric comparison from string comparison. Awk has one operator for both that decides at run time which comparison to do. A2p does not try to do a complete job of awk emulation at this point. Instead it guesses which one you want. It's almost always right, but it can be spoofed. All such guesses are marked with the comment ""#???"". You should go through and check them. You might want to run at least once with the -w switch to perl, which will warn you if you use == where you should have used eq. Perl does not attempt to emulate the behavior of awk in which nonexistent array elements spring into existence simply by being referenced. If somehow you are relying on this mechanism to create null entries for a subsequent for...in, they won't be there in perl. If a2p makes a split line that assigns to a list of variables that looks like (Fld1, Fld2, Fld3...) you may want to rerun a2p using the -n option mentioned above. This will let you name the fields throughout the script. If it splits to an array instead, the script is probably referring to the number of fields somewhere. The exit statement in awk doesn't necessarily exit; it goes to the END block if there is one. Awk scripts that do contortions within the END block to bypass the block under such circumstances can be simplified by removing the conditional in the END block and just exiting directly from the perl script. Perl has two kinds of array, numerically-indexed and associative. Perl associative arrays are called "hashes". Awk arrays are usually translated to hashes, but if you happen to know that the index is always going to be numeric you could change the {...} to [...]. Iteration over a hash is done using the keys() function, but iteration over an array is NOT. You might need to modify any loop that iterates over such an array. Awk starts by assuming OFMT has the value %.6g. Perl starts by assuming its equivalent, $#, to have the value %.20g. You'll want to set $# explicitly if you use the default value of OFMT. Near the top of the line loop will be the split operation that is implicit in the awk script. There are times when you can move this down past some conditionals that test the entire record so that the split is not done as often. For aesthetic reasons you may wish to change index variables from being 1-based (awk style) to 0-based (Perl style). Be sure to change all operations the variable is involved in to match. Cute comments that say "# Here is a workaround because awk is dumb" are passed through unmodified. Awk scripts are often embedded in a shell script that pipes stuff into and out of awk. Often the shell script wrapper can be incorporated into the perl script, since perl can start up pipes into and out of itself, and can do other things that awk can't do by itself. Scripts that refer to the special variables RSTART and RLENGTH can often be simplified by referring to the variables $`, $& and $', as long as they are within the scope of the pattern match that sets them. The produced perl script may have subroutines defined to deal with awk's semantics regarding getline and print. Since a2p usually picks correctness over efficiency. it is almost always possible to rewrite such code to be more efficient by discarding the semantic sugar. For efficiency, you may wish to remove the keyword from any return statement that is the last statement executed in a subroutine. A2p catches the most common case, but doesn't analyze embedded blocks for subtler cases. ARGV[0] translates to $ARGV0, but ARGV[n] translates to $ARGV[$n-1]. A loop that tries to iterate over ARGV[0] won't find it. ENVIRONMENT
A2p uses no environment variables. AUTHOR
Larry Wall <larry@wall.org> FILES
SEE ALSO
perl The perl compiler/interpreter s2p sed to perl translator DIAGNOSTICS
BUGS
It would be possible to emulate awk's behavior in selecting string versus numeric operations at run time by inspection of the operands, but it would be gross and inefficient. Besides, a2p almost always guesses right. Storage for the awk syntax tree is currently static, and can run out. perl v5.12.4 2011-06-01 A2P(1)

Featured Tech Videos

All times are GMT -4. The time now is 01:39 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy