10 More Discussions You Might Find Interesting
1. Shell Programming and Scripting
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)
Discussion started by: garethsays
6 Replies
2. Shell Programming and Scripting
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)
Discussion started by: pasaico
8 Replies
3. Shell Programming and Scripting
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)
Discussion started by: SkySmart
7 Replies
4. UNIX for Dummies Questions & Answers
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)
Discussion started by: Xterra
5 Replies
5. Shell Programming and Scripting
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}'
but it is not working pls tell... (3 Replies)
Discussion started by: abhikamune
3 Replies
6. Shell Programming and Scripting
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)
Discussion started by: fate
2 Replies
7. Shell Programming and Scripting
Actually I got a list of file end with *.txt
I want to use the same command apply to all the *.txt
Thus I try to find out the fastest way to write those same command in a script and then want to let them run automatics.
For example:
I got the file below:
file1.txt
file2.txt
file3.txt... (4 Replies)
Discussion started by: patrick87
4 Replies
8. Shell Programming and Scripting
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)
Discussion started by: senior_ahmed
6 Replies
9. Shell Programming and Scripting
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)
Discussion started by: krishna_gnv
1 Replies
10. UNIX for Dummies Questions & Answers
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)
Discussion started by: gseyforth
12 Replies
PERLTRAP(1) Perl Programmers Reference Guide PERLTRAP(1)
NAME
perltrap - Perl traps for the unwary
DESCRIPTION
The biggest trap of all is forgetting to "use warnings" or use the -w switch; see perllexwarn and perlrun. The second biggest trap is not
making your entire program runnable under "use strict". The third biggest trap is not reading the list of changes in this version of Perl;
see perldelta.
Awk Traps
Accustomed awk users should take special note of the following:
o A Perl program executes only once, not once for each input line. You can do an implicit loop with "-n" or "-p".
o The English module, loaded via
use English;
allows you to refer to special variables (like $/) with names (like $RS), as though they were in awk; see perlvar for details.
o Semicolons are required after all simple statements in Perl (except at the end of a block). Newline is not a statement delimiter.
o Curly brackets are required on "if"s and "while"s.
o Variables begin with "$", "@" or "%" in Perl.
o Arrays index from 0. Likewise string positions in substr() and index().
o You have to decide whether your array has numeric or string indices.
o Hash values do not spring into existence upon mere reference.
o You have to decide whether you want to use string or numeric comparisons.
o Reading an input line does not split it for you. You get to split it to an array yourself. And the split() operator has different
arguments than awk's.
o The current input line is normally in $_, not $0. It generally does not have the newline stripped. ($0 is the name of the program
executed.) See perlvar.
o $<digit> does not refer to fields--it refers to substrings matched by the last match pattern.
o The print() statement does not add field and record separators unless you set $, and "$". You can set $OFS and $ORS if you're using
the English module.
o You must open your files before you print to them.
o The range operator is "..", not comma. The comma operator works as in C.
o The match operator is "=~", not "~". ("~" is the one's complement operator, as in C.)
o The exponentiation operator is "**", not "^". "^" is the XOR operator, as in C. (You know, one could get the feeling that awk is
basically incompatible with C.)
o The concatenation operator is ".", not the null string. (Using the null string would render "/pat/ /pat/" unparsable, because the
third slash would be interpreted as a division operator--the tokenizer is in fact slightly context sensitive for operators like "/",
"?", and ">". And in fact, "." itself can be the beginning of a number.)
o The "next", "exit", and "continue" keywords work differently.
o The following variables work differently:
Awk Perl
ARGC scalar @ARGV (compare with $#ARGV)
ARGV[0] $0
FILENAME $ARGV
FNR $. - something
FS (whatever you like)
NF $#Fld, or some such
NR $.
OFMT $#
OFS $,
ORS $
RLENGTH length($&)
RS $/
RSTART length($`)
SUBSEP $;
o You cannot set $RS to a pattern, only a string.
o When in doubt, run the awk construct through a2p and see what it gives you.
C/C++ Traps
Cerebral C and C++ programmers should take note of the following:
o Curly brackets are required on "if"'s and "while"'s.
o You must use "elsif" rather than "else if".
o The "break" and "continue" keywords from C become in Perl "last" and "next", respectively. Unlike in C, these do not work within a "do
{ } while" construct. See "Loop Control" in perlsyn.
o The switch statement is called "given/when" and only available in perl 5.10 or newer. See "Switch Statements" in perlsyn.
o Variables begin with "$", "@" or "%" in Perl.
o Comments begin with "#", not "/*" or "//". Perl may interpret C/C++ comments as division operators, unterminated regular expressions
or the defined-or operator.
o You can't take the address of anything, although a similar operator in Perl is the backslash, which creates a reference.
o "ARGV" must be capitalized. $ARGV[0] is C's "argv[1]", and "argv[0]" ends up in $0.
o System calls such as link(), unlink(), rename(), etc. return nonzero for success, not 0. (system(), however, returns zero for success.)
o Signal handlers deal with signal names, not numbers. Use "kill -l" to find their names on your system.
Sed Traps
Seasoned sed programmers should take note of the following:
o A Perl program executes only once, not once for each input line. You can do an implicit loop with "-n" or "-p".
o Backreferences in substitutions use "$" rather than "".
o The pattern matching metacharacters "(", ")", and "|" do not have backslashes in front.
o The range operator is "...", rather than comma.
Shell Traps
Sharp shell programmers should take note of the following:
o The backtick operator does variable interpolation without regard to the presence of single quotes in the command.
o The backtick operator does no translation of the return value, unlike csh.
o Shells (especially csh) do several levels of substitution on each command line. Perl does substitution in only certain constructs such
as double quotes, backticks, angle brackets, and search patterns.
o Shells interpret scripts a little bit at a time. Perl compiles the entire program before executing it (except for "BEGIN" blocks,
which execute at compile time).
o The arguments are available via @ARGV, not $1, $2, etc.
o The environment is not automatically made available as separate scalar variables.
o The shell's "test" uses "=", "!=", "<" etc for string comparisons and "-eq", "-ne", "-lt" etc for numeric comparisons. This is the
reverse of Perl, which uses "eq", "ne", "lt" for string comparisons, and "==", "!=" "<" etc for numeric comparisons.
Perl Traps
Practicing Perl Programmers should take note of the following:
o Remember that many operations behave differently in a list context than they do in a scalar one. See perldata for details.
o Avoid barewords if you can, especially all lowercase ones. You can't tell by just looking at it whether a bareword is a function or a
string. By using quotes on strings and parentheses on function calls, you won't ever get them confused.
o You cannot discern from mere inspection which builtins are unary operators (like chop() and chdir()) and which are list operators (like
print() and unlink()). (Unless prototyped, user-defined subroutines can only be list operators, never unary ones.) See perlop and
perlsub.
o People have a hard time remembering that some functions default to $_, or @ARGV, or whatever, but that others which you might expect to
do not.
o The <FH> construct is not the name of the filehandle, it is a readline operation on that handle. The data read is assigned to $_ only
if the file read is the sole condition in a while loop:
while (<FH>) { }
while (defined($_ = <FH>)) { }..
<FH>; # data discarded!
o Remember not to use "=" when you need "=~"; these two constructs are quite different:
$x = /foo/;
$x =~ /foo/;
o The "do {}" construct isn't a real loop that you can use loop control on.
o Use "my()" for local variables whenever you can get away with it (but see perlform for where you can't). Using "local()" actually
gives a local value to a global variable, which leaves you open to unforeseen side-effects of dynamic scoping.
o If you localize an exported variable in a module, its exported value will not change. The local name becomes an alias to a new value
but the external name is still an alias for the original.
As always, if any of these are ever officially declared as bugs, they'll be fixed and removed.
perl v5.18.2 2014-01-06 PERLTRAP(1)