Actually that script was working fine previously, I don't know how suddenly that too many arguments error came up.
Table_name[0]="Emp_table"
For index in "${!Table_name[*]}"; do
Tname="$Table_name[index]"
if [ -f $Tname*.* ]; then
Rm $Tname*.*
fi
done
Here error comming at the if statement.
The same script logic working fine previously, I started implementing the same logic in new script, that time this error came up for both scripts,
I am new to this shell scripting.
Could some one help me understand.
the test, [ and [[ commands all act the same in that
they do different things based on how many arguments they are given
(excluding the closing ]/]]).
with 1 argument, the test will be successful if the argument is not empty
with 2 arguments, the arguments are treated as a unary operator (such as
-n) and an operand.
with 3 arguments, the arguments are treated as an operand, a binary
operator (such as =) and another operand
more than 3 arguments, test and [ give a "too many arguments" error,
and [[ may or may not give an error (it has a more complicated parser).
-f expects a single argument to tell you if that is a file.
$Tname*.* is expanding to multiple arguments.
I think you want to know: are there any files that start with $Tname. Here's one way:
files=( "$Tname"*.* )
if [ ${!files[#]} -ge 1 ] && [ -f "${files[0]}" ]; then ...
That captures the list of files in the files array, and then tests the size of that array.
Related
I have to change permission of a file to 644 if the file does have a different permission than 644.
I have thought of something like this:
if [ $(stat -c %A $soubor) ! -eq (-rw-r--r--) ];then...
However, it gives errors like:
integer expression expected
or if I modify it a little, then:
syntax error):
You're using [ wrong. It's the same as test, so man test gives you the manual page to it.
Basically, [ is a program you call with arguments. For nicer looks, [ requires the last paramter to be ], but there is not technical reason for that.
When you call [ $a == $b ], it fails because [ will compare $a to = and complain about the $b which it does not expect. So if you want to develop it POSIX-compliant, you need to use = instead of ==.
-eq does a numeric compare so -rw-r--r-- will cause a syntax error because it's not numeric.
= will do a string compare, so this is what you need.
You compare with (-rw-r--r--) which will be evaulated as command, so you need to add quotes around it (see my comment on your question, I used the octal syntax).
Also, you need to remove the braces so it becomes '-rw-r--r--'. I assume you added them because they were on the left side of your if statement.
The reason for the braces on the left is command execution. When you wrap something into $(), it will get executed and the output of the command will be filled in there. So after the shell evaluated the expression, it can look like this:
'[' '-rw-rw-rw-' '=' '-rw-r--r--' ']'
When you use set -x anywhere in your shell script, you can see what it acutally does which helps a lot. You can disable it with set +x afterwards as it's very verbose.
I have a .sh file in which I have written the following function. The command that calls this function will have the arguments- file1.war, file2.war ... fileN.war and other arguments.
I want to do a certain operation to the .war files and something else for the arguments after it. So I have written a while loop that will run till the arguments are .war files, and when an argument is encountered without .war extention, it will exit the loop and run the code below it for the rest of the arguments.
Here is the function in .sh file :
copyWarFiles()
{
downloadFileName=$1
shift 1
extn=".war"
while [ condition ]
do
log "war file $downloadFileName .."
#some operation..
downloadFileName=$1
shift 1
done
#operations for the rest of the arguments...
}
What should I give as condition that will return true if $downloadFileName ends with .war? I tried giving
$downloadFileName==*".war" (following the accepted answer in this )
and I also tried this :
`test "${downloadFileName#*$extn}" != "$downloadFileName"`
(following the accepted answer here) where extn is another variable I declared and assigned to .war.
But in both the cases, I see that it never enters the while loop. I think I have gone wrong with the syntax or something. Thank you for your help in advance.
What should I give as condition that will return true if $downloadFileName ends with ".war"? I tried giving $downloadFileName==*".war" […]
Bash, unlike typical programming languages, doesn't recognize == as a special operator; it's just yet another argument to the [ command. So you need to set it off with spaces.
Also, the [ command doesn't support having a pattern on the right-hand-side of ==; you need to use the special [[ ... ]] notation.
So:
while [[ $downloadFileName == *".war" ]]
Note, though, that the double-quotes around .war don't actually have any effect: none of the characters in .war are special characters that need to be quoted. Conversely, it's a best practice to always put variable expansions in double-quotes, in case the variables contain special characters. ([[ actually negates most of the problematic behaviors, but it's just a good habit to be in.)
So:
while [[ "$downloadFileName" == *.war ]]
Why not just:
check=`echo $downloadFile | grep '\.war'`
if [ -n "$check" ]; then
echo $downloadFile ends in .war
fi
I found a nifty little shell script that I wanted to use from this website here. I have followed everything step-by-step, but receive the following error when running this on my CentOS box.
./deploy: line 3: =: command not found
Line 3 only contains...
$ERRORSTRING = "Error. Please make sure you've indicated correct parameters"
I've tried toying around with a bit, but don't understand why it won't accept the "=" character. Is there something wrong with the script, or is it merely something different in the way that my server processes the script?
Thanks!
Gah, that script is full of bad scripting practices (in addition to the outright error you're running into). Here's the outright error:
$ERRORSTRING = "Error. Please make sure you've indicated correct parameters"
As devnull pointed out, this should be:
ERRORSTRING="Error. Please make sure you've indicated correct parameters"
A couple of lines down (and again near the end), we have:
echo $ERRORSTRING;
...which works, but contains two bad ideas: a variable reference without double-quotes around it (which will sometimes be parsed in unexpected ways), and a semicolon at the end of the line (which is a sign that someone is trying to write C or Java or something in a shell script). Use this instead:
echo "$ERRORSTRING"
The next line is:
elif [ $1 == "live" ]
...which might work, depending on whether the value of $1 has spaces, or is defined-but-blank, or anything like that (again, use double-quotes to prevent misparsing!). Also, the == comparison operator is nonstandard -- it'll work, because bash supports it in its [ ... ] builtin syntax, but if you're counting on having bash extensions available, why not use the much cleaner [[ ... ]] replacement? Any of these would be a better replacement for that line:
elif [ "$1" = "live" ]
elif [[ $1 == "live" ]]
elif [[ "$1" == "live" ]]
Personally, I prefer the last. The double-quotes aren't needed in this particular case, but IMO it's safest to just double-quote all variable references unless there's a specific reason not to. A bit further down, there's a elif [ $2 == "go" ] that the same comments apply to.
BTW, there's a good sanity-checking tool for shell scripts at www.shellcheck.net. It's not quite as picky as I am (e.g. it doesn't flag semicolons at the ends of lines), but it pointed out all of the actual errors in this script...
"Devnulls" answer was correct -- I had to remove the spaces around the "=" and remove the "$" from that line as well. The end result was...
ERRORSTRING="Error. Please make sure you've indicated correct parameters"
I've upvoted Devnull and gniourf_gniourf's comments.
Thank you to all whom have assisted!
I'm trying to figure what exactly is the bash code mentioned below trying to do, specially the [-z $M ] part. here M is a variable with a value
if [ -z $M ] ; then
can not find module directory
exit 1
man test Enter
press /-zEnter
you see:
-z STRING
the length of STRING is zero
so your script does, if $M length==0, then exit with status code 1
As others have said, it's using the test command (aka [) to check whether a string is blank. At least, that's what it's trying to do; because the string ($M) isn't double-quoted, it's actually doing something slightly different. Without double-quotes, the value of $M undergoes word splitting and wildcard expansion after it's replaced, so it might not be treated as a simple string (which the -z operator works on) with ... potentially unexpected consequences. Let me run through some of the possibilities:
If the value of $M is a single word (non-blank) without wildcards (* and ?), everything works as expected.
If the value of $M is zero-length (blank), the test command only sees a single argument (-z); when test is only given a single argument, it simply tests whether it's blank -- it's not, so it evaluates to true.
This happens to be the expected result in this case, but it's purely by coincidence, and with many other operators it wouldn't be the right result. For instance, [ -n $M ] (which looks like it should test whether $M is *non*blank), [ -e $M ] (which looks like it should test whether $M is the name of a file/directory) etc will all evaluate to true if $M is blank.
If the value of $M consists entirely of whitespace (but isn't empty), it gets eliminated before test sees it, and test evaluates to true (see previous case). This might or might not be what the scripter had in mind.
If the value of $M has multiple words, test will attempt to evaluate it as (part of) an expression. It will probably not be a valid expression, in which case test will print an error and return false (which is right ... sort of).
On the other hand, if it is a valid expression... Suppose for example you had, M='= -z; test would evaluate the expression -z = -z which would be true, not at all what the scripter had in mind.
If the value of $M has any wildcards, the shell will try to match them against files and pass test the list of matches; it'll try to evaluate them as an expression (see previous case), probably giving an error and returning false (again, sort of right).
Mind you, if you happen to have set the nullglob shell option and the wildcard doesn't match any files, the shell will replace it with null, and the script will act as though "u*n*m*a*t*c*h*e*d" was the empty string.
The lesson here: if you don't want your scripts to behave in weird and unexpected ways, double-quote your variable references!
The [ is actually a standard Unix command (probably implemented internally in Bash, but available whatever shell you are using). It is an alias for the command test, so its manual entry can be found by typing man test. Here's an online copy of that manual page.
When invoked as [, test will generally expect its last argument to be a ], just for good looks, so [ -z $M ] is equivalent to test -z $M.
In this case, the -z argument causes test to return true if the following argument is a string of length zero. The variable $M, defined further up the script, can thus be tested for a valid value.
It checks whether the content of variable M is an empty string.
Check this link
I am trying to read part of a file and stop and a particular line, using bash. I am not very familiar with bash, but I've been reading the manual and various references, and I don't understand why something like the following does not work (but instead produces a syntax error):
while { read -u 4 line } && (test "$line" != "$header_line")
do
echo in loop, line=$line
done
I think I could write a loop that tests a "done" variable, and then do my real tests inside the loop and set "done" appropriately, but I am curious as to 1) why the above does not work, and 2) is there some small correction that would make it work? I still fairly confused about when to use [, (, {, or ((, so perhaps some other combination would work, though I have tried several.
(Note: The "read -u 4 line" works fine when I call it above the loop. I have opened a file on file descriptor 4.)
I think what you want is more like this:
while read -u 4 line && test "$line" != "$header_line"
do
...
done
Braces (the {} characters) are used to separate variables from other parts of a string when whitespace cannot be used. For example, echo "${var}x" will print the value of the variable var followed by an x, but echo "$varx" will print the value of the variable varx.
Brackets (the [] characters) are used as a shortcut for the test program. [ is another name for test, but when test detects that it was called with [ it required a ] as its last argument. The point is clarity.
Parenthesis (the () characters) are used in a number of different situations. They generally start subshells, although not always (I'm not really certain in case #3 here):
Retrieving a single exit code from a series of processes, or a single output stream from a sequence of commands. For example, (echo "Hi" ; echo "Bye") | sed -e "s/Hi/Hello/" will print two lines, "Hello" and "Bye". It is the easiest way to get multiple echo statements to produce a single stream.
Evaluating commands as if they were variables: $(expr 1 + 1) will act like a variable, but will produce the value 2.
Performing math: $((5 * 4 / 3 + 2 % 1)) will evaluate like a variable, but will compute the result of that mathematical expression.
The && operator is a list operator - he seperates two commands and only executes when the first is true, but in this case the first is the while and he is expecting his do stuff. And then he reaches do and the while stuff is already history.
Your intention is to put it into the expression. So you put it together with (). E.g. this a solution with just a small change
while ( read -u 4 line && test "$line" != "$header_line" )