I'm a newbie in perl and I'm trying to execute an operating system command from a Perl script.
The operating system command is executed with IPC::Open3, and the command is like
$cmd = "mycommand --add \"condition LIKE '%TEXT%' \"";
This command is supposed to insert the string contained after the "add" into a database.
The problem is that it inserts the record in the database without the single quotes around %TEXT%, like this:
condition LIKE %TEXT%
If I execute the command at a command prompt it inserts the string correctly.
How should I format the double and single quotes so that it is inserted in the database correctly?
Thanks for the help
By putting the command in a single string, you are inflicting upon it a pass through your system's shell. (You don't mention if it's cmd.exe or bash or other fun stuff.)
Suggestions:
Creating your system command as an array of strings will avoid the shell re-interpolating your command line.
#cmd = ('mycommand', '--add', q(condition LIKE '%TEXT%'));
Throw in extra backslashes to protect the single quotes from your shell. Prepending echo to your command could help with the debugging....
(my personal favorite) Don't shell out for your Database access. use DBI.
$cmd = q{mycommand --add "condition LIKE '%TEXT%'"};
qq is for double-quoting , q is for single quoting.
This way it takes whole command as it is.
Related
I want to open a text file in notepad++ in a particular line number. If I do this in cmdline the command should be:
start notepad++ "F:\Path\test.txt" -n100
And it is working fine from command line. Now I have to do this from tcl. But I can't make this command work with exec. When I try to execute this:
exec "start notepad++ \"F:\Path\test.txt\" -n100"
I am getting this error:
couldn't execute "start notepad++ "F:\Path\test.txt" -n100": no such file or directory.
What am I missing. Please guide.
Similar to this question:
exec {*}[auto_execok start] notepad++ F:/Path/test.txt -n10
First, you need to supply each argument of the command as separate values, instead of a single string/list. Next, to mimic the start command, you would need to use {*}[auto_execok start].
I also used forward slashes instead of backslashes, since you would get a first level substitution and get F:Path est.txt.
EDIT: It escaped me that you could keep the backslashes if you used braces to prevent substitution:
exec {*}[auto_execok start] notepad++ {F:\Path\test.txt} -n10
You can simply surround the entire exec statement in curly braces. Like this:
catch {exec start notepad++.exe f:\Path\test.txt -n10}
I haven't found a perfect solution to this yet. All my execs seem to be different from each other. On windows there are various issues.
Preserving double quotes around filename (or other) arguments.
e.g. in tasklist /fi "pid eq 2060" /nh the quotes are required.
Preserving spaces in filename arguments.
Preserving backslash characters in filename arguments.
[Internally, Windows doesn't care whether pathnames have / or \, but some programs will parse the filename arguments and expect the backslash character].
The following will handle the backslashes and preserve spaces, but will not handle double-quoted arguments. This method is easy to use. You can build up the command line using list and lappend.
set cmd [list notepad]
set fn "C:\\test 1.txt"
lappend cmd $fn
exec {*}$cmd
Using a string variable rather than a list allows preservation of quoted arguments:
set cmd [auto_execok start]
append cmd " notepad"
append cmd " \"C:\\test 1.txt\""
exec {*}$cmd
Note that if you need to supply the full path to the command to be executed, it often needs to be quoted also due to spaces in the pathname:
set cmd "\"C:\\Program Files\\mystuff\\my stuff.exe\" "
I want to create scipt to faciliate producing local text file extracts from Hive.
This is to basically execute commands like below:
hive -e "SET hive.cli.print.header=true;SELECT * FROM dropme"|perl -pe 's/(?:\t|^)\KNULL(?=\t|$)//g'>extract/outbound/dropme.txt
While the above works like a charm I find it quite problematic to implement through the parametrized following script (much simplified):
#!/bin/sh
TNAME=dropme
SQL="SELECT * FROM $TNAME"
echo $SQL
echo "SQL: $SQL"
EXTRACMD="hive -e \"SET hive.cli.print.header=true;$SQL\"|perl -pe 'BEGIN{if(defined(\$_=<ARGV>)){s/\b\w+\.//g;print}}s/(?:\t|^)\KNULL(?=\t|$)//g'>extract/outbound/$TNAME.txt"
echo "CMD: $EXTRACMD";
${EXTRACMD}
When run I get: Exception in thread "main" java.lang.NumberFormatException: For input string: "e"
I know there may be many flavours you can print the text or execute command. For instance the line echo $SQL prints me list of files in the directory instead:
SELECT file1.txt file2.txt file3.txt file4.txt FROM dropme
while the next one: echo "SQL: $SQL" gives just what I want: SQL: SELECT * FROM dropme
echo "CMD: $EXTRACMD" prints the (almost) the command to be executed. Almost, as I see \t in perl code being expanded:
CMD: hive -e "SET hive.cli.print.header=true;SELECT * FROM dropme"|perl -pe 'BEGIN{if(defined($_=<ARGV>)){s\w+\.//g;print}}s/(?: |^)\KNULL(?= |$)//g'>extract/outbound/dropme.txt
Maybe that's still ok, but what I want is to be able to copy&paste this command into (other) terminal and execute as the command I put at the top. Ideally I would like that command to be exactly the same (so with \t there)
Biggest problem I have comes when I try to execute it (${EXTRACMD} line). I'm getting the error:
Exception in thread "main" java.lang.NumberFormatException: For input string: "e" …and so on, irrelevant as bash treats every 'word' as single command here. I assume as I don't even know what is really tries to run (prior print attempt obviously doesn't help)
I'm aware that I have multiple options, like:
escaping special characters in the command definition string (like I did with doublequotes)
experimenting with echo and $VAR, '$VAR' or "$VAR"
experimenting with "${EXTRACMD}" or evaluating through eval "${EXTRACMD}"
experimenting with shopt -s extglob or set -f
but as number of combinations is quite large and with my little bash experience I feel it's better to ask for good practice here so my question is:
Is there a way to print a (complex/compound shell) command first and subsequently be able to execute it (exactly as per printed output)? In this case it would be printing the exact command from the top, then executing it the same way as by manually copying that output into terminal prompt and pressing Enter.
Do not construct commands as strings. See http://mywiki.wooledge.org/BashFAQ/050 for details.
That page also talks about a built-in way of getting the shell to tell you what it is running (section 6).
If that doesn't do what you want you can also, with bash, try using printf %q\\n "${arr[*]}".
I'm trying to put together an SFTP command to be run through Powershell. The executable I have access to is SFTPC.exe (Bitvise Tunnelier)
The command I'm trying is
sftpc.exe user#ftp.domain.com -pw=password -unat=y -cmd="ls \"somefile.txt\""
According to the documentation at https://www.bitvise.com/files/sftpc-v4.14-usage.txt this should log in and run the command ls "somefile.txt" (quotes are escaped within the command parameter)
What actually happens is that I get another line for input, as if there's an unclosed quote.
I've tried adding an extra quote to the end
sftpc.exe user#ftp.domain.com -pw=password -unat=y -cmd="ls \"somefile.txt\"""
This connects and logs in, but the colland it tries to run is ls \somefile.txt"
Note the trailing quote and the leading slash.
So it looks like I'm missing something in the quote escaping, but I can't see what I might be doing wrong. I've also tried replacing double quotes with single in a couple of different places, experiments that usually end in a syntax error.
The escape character in powershell is not a backslash, it's the backtick.
Does the below work?
sftpc.exe user#ftp.domain.com -pw=password -unat=y -cmd="ls `"somefile.txt`""
I am running a T-SQL script, called from a powershell script, that contains a text row which includes a sequence containing $(MV).
When I run the script I get the error "'MV' scripting variable not defined." which I assume is because it interpretates the $(MV) string as a variable instead of being a part of the text string.
How can I write the dollar sign as an escape sequence? Is that possible in a string?
Are you executing the script with sqlcmd? It will interpret $(variablename) and try to expand it.
You can disable this using the -x command-line option.
Oh, if you're using Invoke-Sqlcmd you can use the -DisableVariables parameter.
I was assuming you didn't want to have the sqlcmd variable substitution done. If you were just trying to get the $ past Powershell, use the back-tick (`$) as in another suggestion.
You can use the backtick character to escape a $ sign in PowerShell:
`$
I am trying to run a program like this:
$CMD $ARGS
where $ARGS is a set of arguments with spaces. However, zsh appears to be handing off the contents of $ARGS as a single argument to the executable. Here is a specific example:
$export ARGS="localhost -p22"
$ssh $ARGS
ssh: Could not resolve hostname localhost -p22: Name or service not known
Is there a bash or zsh flag that controls this behavior?
Note that when I put this type of command in a $!/bin/sh script, it performs as expected.
Thanks,
SetJmp
In zsh it's easy:
Use cmd ${=ARGS} to split $ARGS into separate arguments by word (split on whitespace).
Use cmd ${(f)ARGS} to split $ARGS into separate arguments by line (split on newlines but not spaces/tabs).
As others have mentioned, setting SH_WORD_SPLIT makes word splitting happen by default, but before you do that in zsh, cf. http://zsh.sourceforge.net/FAQ/zshfaq03.html for an explanation as to why whitespace splitting is not enabled by default.
If you want to have a string variable (there are also arrays) be split into words before passing to a command, use $=VAR. There is also an option (shwordsplit if I am not mistaking) that will make any command $VAR act like command $=VAR, but I suggest not to set it: I find it very inconvenient to type things like command "$VAR" (zsh: command $VAR) and command "${ARRAY[#]}" (zsh: command $ARRAY).
It will work if you use eval $CMD $ARGS.