The minimum to understand an awk script (Extract from awk man pages) :
Quote:
Files are processed in the following way:
1. The awk command scans its instructions and executes any actions specified
to occur before the input file is read.
2. One record is read from the input file.
3. The record is compared against each pattern specified by the awk command's
instructions.
4. If the record matches a pattern, any actions associated with that pattern
are performed on the record.
5. After the record is compared to each pattern, and all specified actions are
performed, the next record is read from input; the process is repeated
until all records are read from the input file.
6. If multiple input files have been specified, the next file is then opened
and the process repeated until all input files have been read.
7. After the last record in the last file is read, the awk command executes
any instructions specified to occur after the input processing.
The awk command programming language consists of statements in the form:
Pattern { Action }
If a record matches the specified pattern, or contains a field which matches the
pattern, the associated action is then performed. A pattern can be specified
without an action, in which case the entire line containing the pattern is
written to standard output. An action specified without a pattern is performed
for every input record.
The following code :
Can be rewritten like that :
Get_detail isn't a function, it's a variable used as a boolean (0=false, other values=true).
Hi,
I found this command in this forum, but, couldnt understand much from it.
could any one help me understand that???
the commands are :
awk '{sub(/ ~/,""); printf $0 ($0~/\|$/?ORS:"")}' file1 > file2
awk '{sub(/~ */,x);printf $0(/\|$/?ORS:x)}'
awk '{sub(/~ */,x);sub(/\|$/, "|\n")}8'... (4 Replies)
I have a file like this I have to
I have input file this , I want to give the out put in the below
input file
(NARAYANA 1 ENDING AT (100, 16383)
,NARAYANA 2 ENDING AT (100, 32766)
,NARAYANA 3 ENDING AT (100, 49149)
,NARAYANA 4 ENDING AT (100, 65535)
,NARAYANA 5... (8 Replies)
hi buddies
pls help in this matter
i have file like this input file
--------------------------
(PARTITION PARTITION_1 VALUES LESS THAN (101, 16383 ) TABLESPACE PART_1
,PARTITION PARTITION_2 VALUES LESS THAN (101, 32766 ) TABLESPACE PART_2
,PARTITION PARTITION_3 VALUES LESS THAN (101,... (3 Replies)
hi all
i wrote a shell script which uses perl script my code is :
>cat filename | while read i
>do
>perl -e 'require "/home/scripts/abc.pl" ; abc("$i")'
>done
perl script used will simply check syntax of Cobol programs but it didn't work for me so i asked my colleague he suggested... (1 Reply)
can u explain this step by step........plz...will it do the same
for I in *.tar.gz; do
A=`basename $I .tar.gz`
mkdir $A
cp marking-guide ${A}/$A
cd $A
gunzip -c ../$I | tar xf -
cd..
done
thnx
__________________ (2 Replies)
found this handy one liner in another thread which is closed, it does what i need but im trying to understand it. it basically matches the field that contains the value v and prints its position
awk -F, '{for(i=1;i<=NF;i++)if($i==v)print i}' v=yourfield inputfile
my understanding is assign... (3 Replies)
Discussion started by: jack.bauer
3 Replies
LEARN ABOUT ULTRIX
awk
awk(1) General Commands Manual awk(1)Name
awk - pattern scanning and processing language
Syntax
awk [-Fc] [-f prog] [-] [file...]
Description
The command scans each input file for lines that match any of a set of patterns specified in prog. With each pattern in prog there can be
an associated action that will be performed when a line of a file matches the pattern. The set of patterns may appear literally as prog,
or in a file specified as -f prog.
Files are read in order; if there are no files, the standard input is read. The file name `-' means the standard input. Each line is
matched against the pattern portion of every pattern-action statement; the associated action is performed for each matched pattern.
An input line is made up of fields separated by white space. (This default can be changed by using FS, as described below.) The fields
are denoted $1, $2, ... ; $0 refers to the entire line.
A pattern-action statement has the form
pattern { action }
A missing { action } means print the line; a missing pattern always matches.
An action is a sequence of statements. A statement can be one of the following:
if ( conditional ) statement [ else statement ]
while ( conditional ) statement
for ( expression ; conditional ; expression ) statement
break
continue
{ [ statement ] ... }
variable = expression
print [ expression-list ] [ >expression ]
printf format [ , expression-list ] [ >expression ]
next # skip remaining patterns on this input line
exit # skip the rest of the input
Statements are terminated by semicolons, new lines or right braces. An empty expression-list stands for the whole line. Expressions take
on string or numeric values as appropriate, and are built using the operators +, -, *, /, %, and concatenation (indicated by a blank).
The C operators ++, --, +=, -=, *=, /=, and %= are also available in expressions. Variables may be scalars, array elements (denoted x[i])
or fields. Variables are initialized to the null string. Array subscripts may be any string, not necessarily numeric; this allows for a
form of associative memory. String constants are quoted "...".
The print statement prints its arguments on the standard output (or on a file if >file is present), separated by the current output field
separator, and terminated by the output record separator. The statement formats its expression list according to the format. For further
information, see
The built-in function length returns the length of its argument taken as a string, or of the whole line if no argument. There are also
built-in functions exp, log, sqrt, and int. The last truncates its argument to an integer. substr(s, m, n) returns the n-character sub-
string of s that begins at position m. The function sprintf(fmt, expr, expr, ...) formats the expressions according to the format given
by fmt and returns the resulting string.
Patterns are arbitrary Boolean combinations (!, ||, &&, and parentheses) of regular expressions and relational expressions. Regular
expressions must be surrounded by slashes and are as in egrep. Isolated regular expressions in a pattern apply to the entire line. Regu-
lar expressions may also occur in relational expressions.
A pattern may consist of two patterns separated by a comma; in this case, the action is performed for all lines between an occurrence of
the first pattern and the next occurrence of the second.
A relational expression is one of the following:
expression matchop regular-expression
expression relop expression
where a relop is any of the six relational operators in C, and a matchop is either ~ (for contains) or !~ (for does not contain). A condi-
tional is an arithmetic expression, a relational expression, or a Boolean combination of these.
The special patterns BEGIN and END may be used to capture control before the first input line is read and after the last. BEGIN must be
the first pattern, END the last.
A single character c may be used to separate the fields by starting the program with
BEGIN { FS = "c" }
or by using the -Fc option.
Other variable names with special meanings include NF, the number of fields in the current record; NR, the ordinal number of the current
record; FILENAME, the name of the current input file; OFS, the output field separator (default blank); ORS, the output record separator
(default new line); and OFMT, the output format for numbers (default "%.6g").
Options
- Used for standard input file.
-Fc Sets interfield separator to named character.
-fprog Uses prog file for patterns and actions.
Examples
Print lines longer than 72 characters:
length > 72
Print first two fields in opposite order:
{ print $2, $1 }
Add up first column, print sum and average:
{ s += $1 }
END { print "sum is", s, " average is", s/NR }
Print fields in reverse order:
{ for (i = NF; i > 0; --i) print $i }
Print all lines between start/stop pairs:
/start/, /stop/
Print all lines whose first field is different from previous one:
$1 != prev { print; prev = $1 }
Restrictions
There are no explicit conversions between numbers and strings. To force an expression to be treated as a number add 0 to it; to force it
to be treated as a string concatenate "" to it.
See Alsolex(1), sed(1)
"Awk - A Pattern Scanning and Processing Language" ULTRIX Supplementary Documents Vol. II: Programmer
awk(1)