10 More Discussions You Might Find Interesting
1. Shell Programming and Scripting
My file (the output of an experiment) starts off looking like this,
_____________________________________________________________
Subjects incorporated to date: 001
Data file started on machine PKSHS260-05CP
**********************************************************************
Subject 1,... (9 Replies)
Discussion started by: samonl
9 Replies
2. Shell Programming and Scripting
The awk below produces an output with the original header and only the matching lines (which is good), but the output where the original line numbering in the match found on is used. I can not figure out how to sequentially number the output instead of using the original.
I did try to add... (2 Replies)
Discussion started by: cmccabe
2 Replies
3. Shell Programming and Scripting
Hello fellow awkers and seders:
need to figure out a way to ensure a software deployment has completed by checking its trace file in which I can store the deployment results as follows:
echo $testvar
===== Summary - Deploy Result - Start ===== ===== Summary - Deploy Result - End =====... (1 Reply)
Discussion started by: ux4me
1 Replies
4. Shell Programming and Scripting
Hi,
I want to do the following:
Extract some lines from different files and copy them into one file, with the first column being the line number. I do this with
cat file1 file2 file3 |grep 'xxx' |nl > output.file
Works fine. But if I want to add data of interest from a fourth file to the... (2 Replies)
Discussion started by: paracetamol
2 Replies
5. Shell Programming and Scripting
Hello,
I am trying to write a shell script that will create a gnuplot file.
My main problem is that I have a data file with two columns:
1.05929120E+09 5.0000701214792
1.05930096E+09 5.00006386985764
1.05930584E+09 5.00019465404908
1.05931072E+09 5.00031960589719
... (2 Replies)
Discussion started by: pau
2 Replies
6. Shell Programming and Scripting
Hi guys,
got a problem here with sed on the command line.
If i have a string as below:
online xx:wer:xcv: sdf:/asdf/http:https-asdfd
How can i match the pattern "http:" and replace the start of the string to the pattern with null?
I tried the following but it doesn't work:
... (3 Replies)
Discussion started by: DrivesMeCrazy
3 Replies
7. UNIX for Advanced & Expert Users
Problem: I have a lot of files, the files first line should always have 4 spaces before any text. Occasionally some of the files will miss the leading spaces and it's a problem. This is only in the first line.
So if there are 4 spaces then text, do nothing. If there are not 4 spaces, add 4... (2 Replies)
Discussion started by: Vryali
2 Replies
8. Shell Programming and Scripting
I have a simple text file.
I want to number each line in that file .
for example:
My text file is
unix
my file
test
My output should be
1 unix
2 my file
3 test (5 Replies)
Discussion started by: pitagi
5 Replies
9. Shell Programming and Scripting
hello experts,
I need a sed command that remove last 10 characters of a line start from 3rd line.
any suggestions?
Thanks you (7 Replies)
Discussion started by: minifish
7 Replies
10. Shell Programming and Scripting
I have a set of files of multi-line records with the records separated by a blank line. I needed to add a record number to the front of each line followed by a colon and did the following:
awk 'BEGIN {FS = "\n"; RS = ""}{for (i=1; i<=NF; i++)print NR,":",$i}' ~/Desktop/data98-1-25.txt >... (3 Replies)
Discussion started by: RacerX
3 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 out-
put.
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:
* Old awk always has a line loop, even if there are no line actions, whereas new awk does not.
* 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 inte-
ger 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 [...]. Itera-
tion 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 the array base $[ from 1 back to perl's default of 0, but remember to change all array sub-
scripts AND all substr() and index() operations 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]. 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 v5.8.9 2005-03-10 A2P(1)