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 MOJAVE
subst
subst(n) Tcl Built-In Commands subst(n)
__________________________________________________________________________________________________________________________________________________NAME
subst - Perform backslash, command, and variable substitutions
SYNOPSIS
subst ?-nobackslashes? ?-nocommands? ?-novariables? string
_________________________________________________________________DESCRIPTION
This command performs variable substitutions, command substitutions, and backslash substitutions on its string argument and returns the
fully-substituted result. The substitutions are performed in exactly the same way as for Tcl commands. As a result, the string argument
is actually substituted twice, once by the Tcl parser in the usual fashion for Tcl commands, and again by the subst command.
If any of the -nobackslashes, -nocommands, or -novariables are specified, then the corresponding substitutions are not performed. For
example, if -nocommands is specified, command substitution is not performed: open and close brackets are treated as ordinary characters
with no special interpretation.
Note that the substitution of one kind can include substitution of other kinds. For example, even when the -novariables option is speci-
fied, command substitution is performed without restriction. This means that any variable substitution necessary to complete the command
substitution will still take place. Likewise, any command substitution necessary to complete a variable substitution will take place, even
when -nocommands is specified. See the EXAMPLES below.
If an error occurs during substitution, then subst will return that error. If a break exception occurs during command or variable substi-
tution, the result of the whole substitution will be the string (as substituted) up to the start of the substitution that raised the excep-
tion. If a continue exception occurs during the evaluation of a command or variable substitution, an empty string will be substituted for
that entire command or variable substitution (as long as it is well-formed Tcl.) If a return exception occurs, or any other return code is
returned during command or variable substitution, then the returned value is substituted for that substitution. See the EXAMPLES below.
In this way, all exceptional return codes are "caught" by subst. The subst command itself will either return an error, or will complete
successfully.
EXAMPLES
When it performs its substitutions, subst does not give any special treatment to double quotes or curly braces (except within command sub-
stitutions) so the script
set a 44
subst {xyz {$a}}
returns "xyz {44}", not "xyz {$a}" and the script
set a "p} q {r"
subst {xyz {$a}}
returns "xyz {p} q {r}", not "xyz {p} q {r}".
When command substitution is performed, it includes any variable substitution necessary to evaluate the script.
set a 44
subst -novariables {$a [format $a]}
returns "$a 44", not "$a $a". Similarly, when variable substitution is performed, it includes any command substitution necessary to
retrieve the value of the variable.
proc b {} {return c}
array set a {c c [b] tricky}
subst -nocommands {[b] $a([b])}
returns "[b] c", not "[b] tricky".
The continue and break exceptions allow command substitutions to prevent substitution of the rest of the command substitution and the rest
of string respectively, giving script authors more options when processing text using subst. For example, the script
subst {abc,[break],def}
returns "abc,", not "abc,,def" and the script
subst {abc,[continue;expr {1+2}],def}
returns "abc,,def", not "abc,3,def".
Other exceptional return codes substitute the returned value
subst {abc,[return foo;expr {1+2}],def}
returns "abc,foo,def", not "abc,3,def" and
subst {abc,[return -code 10 foo;expr {1+2}],def}
also returns "abc,foo,def", not "abc,3,def".
SEE ALSO
Tcl(n), eval(n), break(n), continue(n)
KEYWORDS
backslash substitution, command substitution, variable substitution
Tcl 7.4 subst(n)