12-05-2010
search for a string in a text file
I want to write a script to check for duplicates
For example: I have a text file with information in the format of /etc/passwd
alice:x:1008:555:William Williams:/home/bill:/bin/bash
bob:x:1018:588:Bobs Boos:/home/bob:/bin/bash
bob:x:1019:528:Robt Ross:/home/bob:/bin/bash
james:x:1012:518:Tilly James:/home/bob:/bin/bash
I want to simply check if there are duplicate users and if there are, output the line to standard error. So in the example above since bob appears twice my output would simply generate something like:
Error duplicate user
bob:x:1018:588:Bobs Boos:/home/bob:/bin/bash
bob:x:1019:528:Robt Ross:/home/bob:/bin/bash
Right now I have a while loop that reads each line and stores each piece of information in a variable using awk -F that is delimited with ":". After storing my username I am not too sure on the best approach to check to see if it already exists.
Some parts of my code:
while read line; do
user=`echo $line | awk -F : '{print $1}'`
match=`grep $user $1`($1 is the txtfile)
if [ $? -ne 0 ]; then
echo "Unique user"
else
echo "Not unique user"
then somehow grep those lines and output it
fi
The matching does not produce the right results
Suggestions?
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LEARN ABOUT PHP
substr_replace
SUBSTR_REPLACE(3) 1 SUBSTR_REPLACE(3)
substr_replace - Replace text within a portion of a string
SYNOPSIS
mixed substr_replace (mixed $string, mixed $replacement, mixed $start, [mixed $length])
DESCRIPTION
substr_replace(3) replaces a copy of $string delimited by the $start and (optionally) $length parameters with the string given in $replace-
ment.
PARAMETERS
o $string
- The input string. An array of strings can be provided, in which case the replacements will occur on each string in turn. In
this case, the $replacement, $start and $length parameters may be provided either as scalar values to be applied to each input
string in turn, or as arrays, in which case the corresponding array element will be used for each input string.
o $replacement
- The replacement string.
o $start
- If $start is positive, the replacing will begin at the $start'th offset into $string. If $start is negative, the replacing will
begin at the $start'th character from the end of $string.
o $length
- If given and is positive, it represents the length of the portion of $string which is to be replaced. If it is negative, it rep-
resents the number of characters from the end of $string at which to stop replacing. If it is not given, then it will default to
strlen( $string ); i.e. end the replacing at the end of $string. Of course, if $length is zero then this function will have the
effect of inserting $replacement into $string at the given $start offset.
RETURN VALUES
The result string is returned. If $string is an array then array is returned.
EXAMPLES
Example #1
Simple substr_replace(3) examples
<?php
$var = 'ABCDEFGH:/MNRPQR/';
echo "Original: $var<hr />
";
/* These two examples replace all of $var with 'bob'. */
echo substr_replace($var, 'bob', 0) . "<br />
";
echo substr_replace($var, 'bob', 0, strlen($var)) . "<br />
";
/* Insert 'bob' right at the beginning of $var. */
echo substr_replace($var, 'bob', 0, 0) . "<br />
";
/* These next two replace 'MNRPQR' in $var with 'bob'. */
echo substr_replace($var, 'bob', 10, -1) . "<br />
";
echo substr_replace($var, 'bob', -7, -1) . "<br />
";
/* Delete 'MNRPQR' from $var. */
echo substr_replace($var, '', 10, -1) . "<br />
";
?>
Example #2
Using substr_replace(3) to replace multiple strings at once
<?php
$input = array('A: XXX', 'B: XXX', 'C: XXX');
// A simple case: replace XXX in each string with YYY.
echo implode('; ', substr_replace($input, 'YYY', 3, 3))."
";
// A more complicated case where each replacement is different.
$replace = array('AAA', 'BBB', 'CCC');
echo implode('; ', substr_replace($input, $replace, 3, 3))."
";
// Replace a different number of characters each time.
$length = array(1, 2, 3);
echo implode('; ', substr_replace($input, $replace, 3, $length))."
";
?>
The above example will output:
A: YYY; B: YYY; C: YYY
A: AAA; B: BBB; C: CCC
A: AAAXX; B: BBBX; C: CCC
NOTES
Note
This function is binary-safe.
SEE ALSO
str_replace(3), substr(3), String access and modification by character.
PHP Documentation Group SUBSTR_REPLACE(3)