1. The usage of curly braces {} and " " in displaying variable value - when we use which one?
echo "${filename}"
I have got into the habit of always putting quotes round string variables and strings because it prevents so many silly errors when a value contains spaces.
I have also got into the habit of using curly braces even when they are not strictly necessary because it makes the variable name totally unambiguous.
It also prevents errors like this:
2. use of back quote in value assignment to a variable and with expr command. For eg, the way I'm assigning tot_rec_count.
Quote:
act_rec_count=`expr ${tot_rec_count} - 1`
In ksh and Posix Shell whatever is between backticks is to be executed.
This more modern syntax is preferred. $((arithmetic)).
Also, I wouldn't bother with an array.
Quote:
set -A folders horizon mysteryshopper rcc reference
echo ${folders[@]}
for i in ${folders[@]}
This works the same and imho is easier to read and easier to type:
i want to get a substring from a string and used such shell script:
var_year=`expr substr "07132006" 5 4`
echo $var_year
but i got such error message: expr: syntax error. why?
Note: Kshell used on solaris 8. :confused: (5 Replies)
I found below script to check whether the variable is a digit in ksh.
############################
#!/bin/ksh
REPLY="3f"
if ]*\)'` != ${REPLY} && "${REPLY}" != "0" ]]
then
print "is digit\n"
else
print "not digit\n"
fi
############################
Although it works fine, but... (6 Replies)
I am trying to run the script bellow but its given me "syntax error at line 20 :'done' unexpected." error message"
can someone check to see if the script is ok? and correct me pls.
Today is my first day with scripting.
Gurus should pls help out
#!/bin/ksh
# Purpose: Check to see if file... (3 Replies)
I know I asked a similar question but I want to know if there is a regular expression existing that with a korn shell cmd, finds any timestamp data records in a file where it is greater then a timestamp in a shell variable ?
something like :
grep all records where it has a timestamp >... (5 Replies)
Hi Guys,
THis is the first time am using the expr expression.
I like to know how to write the expression a=(b\100)*a.
THis works fine if it gives without a bracket. the bracket should be present as i wanted to define the order of execution.
Help me out.
Thanks for your help in advance.... (2 Replies)
hello to everyone,
i am writing a shell script in unix and i use the following command:
lnum= cut -f 1 -d : aa
passline=`expr $lnum + 1`
echo "$passline"
with the following command i get the value that is stored in the first field of the file "aa" and i save it in the variable "lnum". i am... (2 Replies)
Hi All,
This is a piece of code from one of my scripts:
t1=`cat temp3.21447 | grep WEALTHTOUC_TRANS_20100409_233127.txt.txt.TRG | awk '{print $3}' | cut -c1-5`
t2=`cat temp3.21447 | grep WEALTHTOUC_TRANS_20100409_233127.txt.txt.TRG | awk '{print $5}' | cut -c1-5`
#t1=23:43... (5 Replies)
Hi All,
As per my knowledge in unix, my code looks fine. But still I am getting error (expr:syntax error). Please help me to resolve this error.
Script :
PRE_LBNO=0
PRE_DATE=0
TOT_PAY=0
TOT_REM=0
TOTAL=1
for Record_Type in `cut -c 1 Inputt.dat`
do
if ;
then
CURR_LBNO=` cut -c... (6 Replies)
This really puzzles me. The following code gives me the error 'expr: syntax error' when I try to do multi-line comment using here document
<<EOF
echo "Sum is: `expr $1 + $2`"
EOF
Even if I explicitly comment out the line containing the expr using "#", the error message would still exist... (3 Replies)
Hi,
I tried to look up the issue i'm experiencing, but i'm confused what's wrong with my script.
After executing the script I'm getting the following error
expr: non-numeric argument
syntax error on line 1, teletype
After some research, it seems that the problem relates to bc.
I have... (1 Reply)
Discussion started by: nms
1 Replies
LEARN ABOUT OPENSOLARIS
expr
expr(1B) SunOS/BSD Compatibility Package Commands expr(1B)NAME
expr - evaluate arguments as a logical, arithmetic, or string expression
SYNOPSIS
/usr/ucb/expr argument...
DESCRIPTION
The expr utility evaluates expressions as specified by its arguments. After evaluation, the result is written on the standard output. Each
token of the expression is a separate argument, so terms of the expression must be separated by blanks. Characters special to the shell
must be escaped. Note: 0 is returned to indicate a zero value, rather than the null string. Strings containing blanks or other special
characters should be quoted. Integer-valued arguments may be preceded by a unary minus sign. Internally, integers are treated as 32-bit,
two's-complement numbers.
The operators and keywords are listed below. Characters that need to be escaped are preceded by `'. The list is in order of increasing
precedence, with equal precedence operators grouped within {} symbols.
expr | expr
Returns the evaluation of the first expr if it is neither NULL nor 0; otherwise, returns the evaluation of the second expr if it is not
NULL; otherwise, 0.
expr & expr
Returns the first expr if neither expr is NULL or 0, otherwise returns 0.
expr { =, , , <, <=, != } expr
Returns the result of an integer comparison if both arguments are integers, otherwise returns the result of a lexical comparison.
expr { +, - } expr
Addition or subtraction of integer-valued arguments.
expr { , /, % } expr
Multiplication, division, or remainder of the integer-valued arguments.
string : regular-expression
match string regular-expression
The two forms of the matching operator above are synonymous. The matching operators : and match compare the first argument with the
second argument which must be a regular expression. Regular expression syntax is the same as that of regexp(5), except that all pat-
terns are "anchored" (treated as if they begin with ^) and therefore ^ is not a special character, in that context. Normally, the
matching operator returns the number of characters matched (0 on failure). Alternatively, the ... pattern symbols can be used to
return a portion of the first argument.
substr string integer-1 integer-2
Extracts the substring of string starting at position integer-1 and of length integer-2 characters. If integer-1 has a value greater
than the length of string, expr returns a null string. If you try to extract more characters than there are in string, expr returns all
the remaining characters from string. Beware of using negative values for either integer-1 or integer-2 as expr tends to run forever
in these cases.
index string character-list
Reports the first position in string at which any one of the characters in character-list matches a character in string.
length string
Returns the length (that is, the number of characters) of string.
( expr )
Parentheses may be used for grouping.
EXAMPLES
Example 1 Adding an integer to a shell variable
Add 1 to the shell variable a.
a='expr $a + 1'
Example 2 Returning a path name segment
Return the last segment of a path name (that is, the filename part). Watch out for / alone as an argument: expr will take it as the divi-
sion operator (see BUGS below).
# 'For $a equal to either "/usr/abc/file" or just "file"'
expr $a : '.*/ $a
Example 3 Using // characters to simplify the expression
The addition of the // characters eliminates any ambiguity about the division operator and simplifies the whole expression.
# A better representation of example 2.
expr //$a : '.*/
Example 4 Returning the value of a variable
Returns the number of characters in $VAR.
expr $VAR : '.*'
EXIT STATUS
expr returns the following exit codes:
0 If the expression is neither NULL nor 0.
1 If the expression is NULL or 0.
2 For invalid expressions.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWscpu |
+-----------------------------+-----------------------------+
SEE ALSO sh(1), test(1), attributes(5), regexp(5)DIAGNOSTICS
syntax error for operator/operand errors
non-numeric argument if arithmetic is attempted on such a string
division by zero if an attempt to divide by zero is made
BUGS
After argument processing by the shell, expr cannot tell the difference between an operator and an operand except by the value. If $a is an
=, the command:
expr $a = '='
looks like:
expr = = =
as the arguments are passed to expr (and they will all be taken as the = operator). The following works:
expr X$a = X=
Note: the match, substr, length, and index operators cannot themselves be used as ordinary strings. That is, the expression:
example% expr index expurgatorious length
syntax error
example%
generates the `syntax error' message as shown instead of the value 1 as you might expect.
SunOS 5.11 6 Jun 2000 expr(1B)