In Windows Command Line I normally write empty line in a file with
echo; >> file
However, what I have now is a variable
$param1%
If I want echo to write it in the file I have to do
echo %param1% >> file
HERE IS WHERE THE PROBLEM START :
If I'd like an empty like I'd make
set param1=;
However since the ; is not in contact with the echo word the command is
echo ; >> file
which write the ; in the file...
I need the variable to sometime contains text, and sometime nothing. How can I do it?
if "%param1%"=="" echo;>>file else echo %param1%>>file
If a param1 variable does not exist (the same as set "param1="), then %param1% results to:
In a .bat script: %param1% results to an empty string (a string of zero length);
In a CLI window: %param1% results to the %param1% string.
In a .bat script use (note no spaces surrounding %param1%)
>> file (echo;%param1%)
In a CLI window use
>>file (if not defined param1 (echo;) else echo;%param1%)
Note proper using of parentheses in if-else! For instance, check interesting result of next command:
if ""=="" echo;"THEN branch">>file else echo;"ELSE branch">>file
Output:
==>if ""=="" echo;"THEN branch">>file else echo;"ELSE branch">>file
==>type file
"THEN branch" else echo;"ELSE branch"
Related
Code snippet:
my $node = shift;
my $runCmd = "cmviewcl -v -f line -p ".$package_name." | awk -F \"[:|=]\" \'(\$1 == \"script_log_file\") { print \$2 }\'";
my $logfile = $output[0];
chomp $logfile;
#DC1_list = utils::getDC1Host($hash_ref);
#DC2_list = utils::getDC2Host($hash_ref);
foreach $node1 (#DC1_list) {
$runCmd = "cmexec $node1 echo \"\" > ".$logfile;
Please let me know the what's this line means:
$runCmd = "cmexec $node1 echo \"\" > ".$logfile;
it was written before as:
$runCmd = "cmexec $node1 rm -rf ".$logfile;
which probably means remove the file in logfile variable forced recursive, but later changed to the above. so
what's it's doing?
Remove a file is different than an empty file.
The first option keep the file but override the content with "" (2x double quote), the second one remove the file.
Maybe your application need the file exist, because of this you cannot remove it.
If you have really copied this line verbatim, it is pretty nonsense.
Let's assume that the variables mentioned here have the folllowing values:
runCmd has value FOO
node1 has value BAR
logfile has value BAZ
After parameter expansion and making the quoting a bit more legible, this leaves you with a line equivalent to
FOO = 'cmexec BAR echo "" >' .BAZ
This means that a command named FOO is invoked. It must either be an executable file in the PATH, or a function. This command gets three parameters:
First parameter : a lonely equal sign
Second parameter: The string cmexec BAR echo "" >
Third paramete : the string .BAZ
I don't believe that anybody would seriously write such a command; my guess is that you made a typo, or error when doing a copy&paste of this command.
First of all I'm trying to obtain a certain property from a KML file. For now, I tried
ogrinfo C:/test.kml -so -al | findstr "Extent"
which was recommended to me and outputs
Extent: (-100.054053, 33.702234) - (-94.647180, 37.125712)
I would require this in the form
-100.054053,-94.647180,33.702234,37.125712 for which I thought to use regex.
I tried the following just to see what it outputted:
ogrinfo C:/test.kml -so -al | findstr "Extent" | findstr /r /c:"-*[0-9]*\.[0-9]*"
but this still outputs
Extent: (-100.054053, 33.702234) - (-94.647180, 37.125712)
I read somewhere that Windows' FINDSTR only outputs the line where it matched and not the regex matches themselves. Is there some other way of doing it?
If I get that working I would save the matches in different variables somehow in a shell script. I'm no expert in shell scripting but I've been looking around and was thinking of doing something like this
#!/bin/bash
for /f "tokens=*" %%a in ('ogrinfo C:/test.kml -so -al ^| findstr "Extent" ^| findstr /r /c:"-*[0-9]*\.[0-9]*"') do (
echo %%a
#do something
)
done >output
but running this causes the shell to immediately disappears and can't even see the error.
Assumptions
You have a kml file with raw data.
You can extract a single line which starts with "Extent: " to get the values you want
Single line => there is only 1 line with that format in the kml file
The format of that line is:
Extent: (NUMBER1, NUMBER2) - (NUMBER3, NUMBER4)
A number can have the following characters: 0 1 2 3 4 5 6 7 8 9 . -
The output you want is:
NUMBER1,NUMBER3,NUMBER2,NUMBER4
Using Linux tools only, you can do this:
#!/bin/bash
#
datafile="data.kml"
# Ensure the data file exists
if [[ ! -f "$datafile" ]]
then
echo "ERROR: the data file does not exist."
exit 1
fi
# Extract the "Extent:" line
dataline=$(grep "Extent: " "$datafile")
# Make sure the line is of a valid format, and assign the number variables
if [[ $dataline =~ "Extent: ("([0-9.-]+)", "([0-9.-]+)") - ("([0-9.-]+)", "([0-9.-]+)")" ]] && number1="${BASH_REMATCH[1]}" && number2="${BASH_REMATCH[2]}" && number3="${BASH_REMATCH[3]}" && number4="${BASH_REMATCH[4]}"
then
echo "-----DEBUG-----"
echo "line==$dataline"
echo "1==$number1"
echo "2==$number2"
echo "3==$number3"
echo "4==$number4"
echo "-- END DEBUG --"
echo ""
echo "$number1,$number3,$number2,$number4"
else
echo "ERROR: there is no \"Extent: \" line in the data file ($datafile)"
fi
Details:
Everything is done in the if line.
=~ matches the left side with the pattern on the right side.
In the regular expression, you can define sections you want to reuse with ( ).
Ex: abcd(1)efgh(2)ijkl. The sections you can reuse are 1 and 2.
So in the if, each number is surrounded by parentheses.
When the =~ is processed, the BASH_REMATCH array is defined with each section.
The "DEBUG" echo statements can be removed or commented out.
If you have more than one "Extent: ..." in the KML file, you can loop on the lines and process each one at a time.
I am trying to debug a bash shell script where I am trying to surround a string/variable with single quotes. I am seeing the following results and am stumped on how to debug this. It obviously has something to do with the content of the variable. I thought the variable may be an array hence some of the echo statements. IN_JSON is being constructed via calls to "jq" to construct some JSON.
echo "IN_JSON = ${IN_JSON}"
echo "IN_JSON = ${IN_JSON[*]}"
echo "IN_JSON = '${IN_JSON[*]}'"
echo "IN_JSON = '" ${IN_JSON} "'"
echo "${#IN_JSON[#]}"
Output:
IN_JSON = {"name":"RX-CLAIM-FILLED"}
IN_JSON = {"name":"RX-CLAIM-FILLED"}
'N_JSON = '{"name":"RX-CLAIM-FILLED"}
'_JSON = ' {"name":"RX-CLAIM-FILLED"}
1
What's going on here and how do I troubleshoot this? It obviously has something to do with the contents of IN_JSON, but I'm not sure why or what is going on here.
The expansion of ${IN_JSON[*]} contains a carriage return character that resets the position of the cursor to beginning of the line, so that the next character ' is printed on beginning of the line.
Most probably, you want to run your file via dos2unix.
So I read the easiest way to use .conf files for bash scripts is to use source to load such files. Now, what if I want to edit this file ?
Some code I found does a really good job :
function set_config(){
sed -i "s/^\($1\s*=\s*\).*\$/\1$2/" $conf_file
}
But, if the variable is not yet defined, it doesn't define it, nor does it check if the parameters are passed well, isn't secure, doesn't handle default values etc...
Does reliable tools/code already exists to edit .conf file which contain key="value" pairs ? For instance, I would like to be able to do things like this :
$conf_file="my_script.conf"
conf_load $conf_file #should create the file if it doesn't exist !
read=$(conf_get_value "data" "default_value") #should read the value with key "data", defaulting to "default_value"
if [[ $? = 0 ]] #we should be able to know if the read was successful
then
echo "Successfully read value for field \"data\" : $read"
else
echo "Default value for field \"data\" : $read"
fi
conf_set "something_new" "a great value!" #should add the key "something_new" as it doesn't exist
conf_set "data" "new_value" #should edit the value with key "data"
if [[ $? = 0 ]]
then
echo "Edit successful !"
else #something went wrong :-/
echo "Edit failed !"
fi
before running this code, the conf file would contain
data="some_value"
and after it would be
data="new_value"
something_new="a great value!"
and the code should output
Successfully read value for field "data" : some_value
Edit successful !
I am using bash version 4.3.30 .
Thanks for your help.
I'd to that with awk since it's rather good at tokenizing:
# overwrite config's entries for KEY with VALUE or else appends the definition
# Usage: set_config KEY VALUE
set_config() {
[ -n "$1" ] && awk -F= -v key="$1" -v new="$1=\"$2\"" '
$1 == key { $0 = new; key_found = 1; }
{ print }
END { if (!key_found) { print new; }
' "$conf_file" > "$conf_file.new" \
&& cat "$conf_file.new" > "$conf_file" && rm "$conf_file.new"
}
If run without arguments, set_config() will do nothing and return false. If run with only one argument, it will create an empty value (outputting KEY="").
The awk command parses the .conf file line by line, looking for each definition of the given key and altering it to the new value. All lines are then printed (with or without modification), preserving the original order. If the key hasn't yet been found by the end of the file, this appends the new definition.
Because you can't pipe a file atop itself, this gets saved with a ".new" extension and then copied atop the original in a manner that preserves permissions. The ".new" copy is then removed. I used && to ensure that these never happen if an error occurred earlier in the function.
Also note that the type of ".conf file" you're referring to (the type you source with a POSIX shell) will never have spaces around its equals signs, so the \s* parts of your sed command aren't needed.
In my program I am trying to return a value from a function, the return value is string. Everything works fine(atleast some part), if I echo the value once it is returned, but it is not even calling the function, if I dont return.... Consider the code below....
#!/bin/bash
function get_last_name() {
echo "Get Last Name"
ipath=$1
IFS='/'
set $ipath
for item
do
last=$item
done
echo $last
}
main() {
path='/var/lib/iscsi/ifaces/iface0'
current=$(get_last_name "$path")
echo -n "Current="
echo $current
}
main
It gives me an output like this
OUTPUT
Current=Get Last Name iface0
If I comment the echo $current, then the I am not even seeing the "Get Last Name", which makes to come to conclusion, that it is not even calling the function. Please let me know what mistake I am making. But one thing I am sure, bash is the ugliest language I have ever seen.......
Functions do not have return values in bash. When you write
current=$(get_last_name "$path")
you are not assigning a return value to current. You are capturing the standard output of get_last_name (written using the echo command) and assigning it to current. That's why you don't see "Get last name"; that text does not make it to the terminal, but is stored in current.
Detailed explanation
Let's walk through get_last_name first (with some slight modifications to simplify the explanation):
function get_last_name () {
ipath=$1
local IFS='/'
set $ipath
for item
do
last=$item
done
echo "Get Last Name"
echo $last
}
I added the local command before IFS so that the change is confined to the body of get_last_name, and I moved the first echo to the end to emphasize the similarity between the two echo statements. When get_last_name is called, it processes its single argument (a string containing a file path), then echoes two strings: "Get Last Name" and the final component of the file path. If you were to run execute this function from the command line, it would appear something like this:
$ get_last_name /foo/bar/baz
Get Last Name
baz
The exit code of the function would be the exit code of the last command executed, in this case echo $last. This will be 0 as long as the write succeeds (which it almost certainly will).
Now, we look at the function main, which calls get_last_name:
main() {
path='/var/lib/iscsi/ifaces/iface0'
current=$(get_last_name "$path")
echo -n "Current="
echo $current
}
Just like with get_last_name, main will not have a return value; it will produce an exit code which is the exit code of echo $current. The function begins by calling get_last_name inside a command substitution ($(...)), which will capture all the standard output from get_last_name and treat it as a string.
DIGRESSION
Note the difference between the following:
current=$(get_last_name "$path")
sets the value of current to the accumulated standard output of get_last_name. (Among other things, newlines in the output are replaced with spaces, but the full explanation of how whitespace is handled is a topic for another day). This has nothing to do with return values; remember, the exit code (the closet thing bash has to "return values") is a single integer.
current=get_last_name "$path"
would not even call get_last_name. It would interpret "$path" as the name of a command and try to execute it. That command would have a variable current with the string value "get_last_name" in its environment.
The point being, get_last_name doesn't "return" anything that you can assign to a variable. It has an exit code, and it can write to standard output. The $(...) construct lets you capture that output as a string, which you can then (among other things) assign to a variable.
Back to main
Once the value of current is set to the output generated by get_last_name, we execute
two last echo statements to write to standard output again. The first writes "Current=" without a newline, so that the next echo statement produces text on the same line as the first. The second just echoes the value of current.
When you commented out the last echo of main, you didn't stop get_last_name from being executed (it had already been executed). Rather, you just didn't print the contents of the current variable, where the output of get_last_name was placed rather than on the terminal.