10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
OK, so I am trying to use awk as a method of accessing a table stored in a file to then provide the capability of a look up table.
The table is stored in a file named "/Users/jhaney/Desktop/assetTypeMapping.tsv" and looks like this:
aCategory aLetter aNumber
AssetCat1 A 123 ... (10 Replies)
Discussion started by: jhaneyzz
10 Replies
2. Shell Programming and Scripting
On AIX 5.3 and AIX 6.1, I have this script for checking printers being pingable or not.
for i in `lsallq`
do
echo "Queue Name: " $i
echo "----------------------------------------"
for j in `lsallqdev -q $i`
do
echo " Device Name:" $j
hname=`echo... (3 Replies)
Discussion started by: Daniel Gate
3 Replies
3. Shell Programming and Scripting
Hi All,
I am using the below script which has awk command, but it is not returing the expected result. can some pls help me to correct the command.
The below script sample.ksh should give the result if the value of last 4 digits in the variable NM matches with the variable value DAT. The... (7 Replies)
Discussion started by: G.K.K
7 Replies
4. Shell Programming and Scripting
Hi all,
i am trying to use below command to see the output of hardware inventory, but i only see 2 first line no output of the command.
awk '/Hardware/ {print $0}' XXX_result.txt
Hardware inventory:
Hardware inventory:
any idea how to see whatever is under hardware inventory.
i... (11 Replies)
Discussion started by: Jared
11 Replies
5. Shell Programming and Scripting
Hi Gurus,
I am facing a similar issue usiung an awk command. Below is my requirement:
---DATA---
A;F;G
A;D;E
A;D;E
B;Z;P
C;Z;Q
Expected:
A
F<TAB>G
D<TAB>E
D<TAB>E
B
D<TAB>E (1 Reply)
Discussion started by: rajangupta2387
1 Replies
6. Shell Programming and Scripting
Hey,
this is my code,
cat $fulltrpath | while read line
do
inputfile=$(sed 1q $fulltrpath | awk '{ FS = "\t"; print $2$1}')
outputpath=$(sed 1q $fulltrpath | awk '{ FS = "\t"; print $3 }')
echo $inputfile
echo $outputpath
cp $inputfile $outputpath
let path++
done
if i... (1 Reply)
Discussion started by: inshafccna
1 Replies
7. Shell Programming and Scripting
Hi guys,
i am trying to analyze a text file using awk and am not able to solve this issue.
This is the piece of code that I have written
BEGIN {
## Time to count MACs -> 5 seconds.
TIME_LIMIT = 5;
k = 50000;
}
## For every line.
{
time_in_seconds = $1... (2 Replies)
Discussion started by: jamie_123
2 Replies
8. Shell Programming and Scripting
I have this input file
0FB7,1083,Synchronized,FriNov121655,2816_7RAID5,05F:1_10F:1,10000000NoneNone,DC_db00p01
0FB7,1150,Split,MonApr180658,2816_7R5GC,N/A,N/A,N/A
06C4,0710,Synchronized,WedMar91105,2816_7RAID5,04E:1_11E:1,10000000NoneNone,DL_nb00p25... (1 Reply)
Discussion started by: greycells
1 Replies
9. Shell Programming and Scripting
In the following code, Im trying to imbed many statements in a single awk statement. But it gives an error on that,
for i in `less usage_types_dwh.txt`
do
cd /u01/app/evident/analysis_lab/usg_type
grep $i svc_type.txt | head -1 | awk 'BEGIN {FS=","} {print $1 "==" $2 ":" $3 ":" $4;... (2 Replies)
Discussion started by: alishehzadpaul
2 Replies
10. Shell Programming and Scripting
Hi,
# grep "^Listen" httpd.conf | awk '{print $2}'
FrontEnd_1_IP:8081
FrontEnd_2_IP:8081
8081
8082
8083
#
I need to get the values one at a time but I just can't manage to do that.
Thanks,
Bianca (20 Replies)
Discussion started by: potro
20 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)