Is there an option for the qemu-nbd command to get the next free, i.e. unused NBD like losetup -f does? The manpage of 0.0.1 (which is version of the currently stable release 1.7.0 of qemu) doesn't mention anything.
You can query attributes about nbd devices in sysfs.
For example:
cat /sys/class/block/nbd0/size
Will return 0, or the size of the mapped image file otherwise, if /dev/ndb0 is in use.
So you could iterate each device until you find one with 0 and attempt to try that with qemu-nbd.
Something like this should do it:
for x in /sys/class/block/nbd* ; do
S=`cat $x/size`
if [ "$S" == "0" ] ; then
qemu-nbd -c /dev/`basename $x` some_file.img
break
fi
done
Related
I'm trying to take the contents of a config file (JSON format), strip out extraneous new lines and spaces to be concise and then assign it to an environment variable before starting my application.
This is where I've got so far:
pwr_config=`echo "console.log(JSON.stringify(JSON.parse(require('fs').readFileSync(process.argv[2], 'utf-8'))));" | node - config.json | xargs -0 printf '%q\n'` npm run start
This pipes a short node.js app into the node runtime taking an argument of the file name and it parses and stringifies the JSON file to validate it and remove any unnecessary whitespace. So far so good.
The result of this is then piped to printf, or at least it would be but printf doesn't support input in this way, apparently, so I'm using xargs to pass it in in a way it supports.
I'm using the %q formatter to format the string escaping any characters that would be a problem as part of a command, but when calling printf through xargs, printf claims it doesn't support %q. I think this is perhaps because there is more than one version of printf but I'm not exactly sure how to resolve that.
Any help would be appreciated, even if the solution is completely different from what I've started :) Thanks!
Update
Here's the output I get on MacOS:
$ cat config.json | xargs -0 printf %q
printf: illegal format character q
My JSON file looks like this:
{
"hue_host": "192.168.1.2",
"hue_username": "myUsername",
"port": 12000,
"player_group_config": [
{
"name": "Family Room",
"player_uuid": "ATVUID",
"hue_group": "3",
"on_events": ["media.play", "media.resume"],
"off_events": ["media.stop", "media.pause"]
},
{
"name": "Lounge",
"player_uuid": "STVUID",
"hue_group": "1",
"on_events": ["media.play", "media.resume"],
"off_events": ["media.stop", "media.pause"]
}
]
}
Two ways:
Use xargs to pick up bash's printf builtin instead of the printf(1) executable, probably in /usr/bin/printf(thanks to #GordonDavisson):
pwr_config=`echo "console.log(JSON.stringify(JSON.parse(require('fs').readFileSync(process.argv[2], 'utf-8'))));" | node - config.json | xargs -0 bash -c 'printf "%q\n"'` npm run start
Simpler: you don't have to escape the output of a command if you quote it. In the same way that echo "<|>" is OK in bash, this should also work:
pwr_config="$(echo "console.log(JSON.stringify(JSON.parse(require('fs').readFileSync(process.argv[2], 'utf-8'))));" | node - config.json )" npm run start
This uses the newer $(...) form instead of `...`, and so the result of the command is a single word stored as-is into the pwr_config variable.*
Even simpler: if your npm run start script cares about the whitespace in your JSON, it's fundamentally broken :) . Just do:
pwr_config="$(< config.json)" npm run start
The $(<...) returns the contents of config.json. They are all stored as a single word ("") into pwr_config, newlines and all.* If something breaks, either config.json has an error and should be fixed, or the code you're running has an error and needs to be fixed.
* You actually don't need the "" around $(). E.g., foo=$(echo a b c) and foo="$(echo a b c)" have the same effect. However, I like to include the "" to remind myself that I am specifically asking for all the text to be kept together.
Hi & thanks in advance.
I'm trying to update a column(version) on an MySQL table from a Bash script.
I've populated a variable with the version numbers, but it fails after applying the first version in the list.
CODE:
UP_VER=`seq ${DB_VER} ${LT_VER} | sed '1d'`
UP_DB=`echo "UPDATE client SET current_db_vers='${UP_VER}' WHERE client_name='${CLIENT}'" | ${MYSQL_ID}`
while read -r line
do
${UP_DB}
if [[ "${OUT}" -eq "0" ]]; then
echo "Database upgraded.."
else
echo "Failed to upgrade.."
exit 1
fi
done < "${UP_VER}"
Thanks
Hopefully solved... My $UP_VER is in a a row not a column.
You're misunderstanding what several shell constructs do:
var=`command` # This executes the command immediately, and stores
# its result (NOT the command itself) in the variable
... < "${UP_VER}" # Treats the contents of $UP_VER as a filename, and tries
# to use that file as input
if [[ "${OUT}" -eq "0" ]]; then # $OUT is not defined anywhere
... current_db_vers='${UP_VER}' ... # this sets current_db_vers to the entire
# list of versions at once
Also, in the shell it's best to use lowercase (or mixed-case) variable names to avoid conflicts with the variables that have special meanings (which are all uppercase).
To fix the first problem, my recommendation is don't try to store shell commands in variables, it doesn't work right. (See BashFAQ #50: I'm trying to put a command in a variable, but the complex cases always fail!.) Either use a function, or just write the command directly where it's going to be executed. In this case I'd vote for just putting it directly where it's going to be executed. BTW, you're making the same mistake with ${MYSQL_ID}, so I'd recommend fixing that as well.
For the second problem, you can use <<< "${UP_VER}" to feed a variable's contents as input (although this is a bashism, and not available in generic posix shells). But in this case I'd just use a for loop:
for ((ver=db_ver+1; ver<=lt_ver; ver++)); do
For the third problem, the simplest way to test the success of a command is to put it directly in the if:
if somecommand; then
echo "Database upgraded.."
else # ... etc
So, here's my take at a rewrite:
mysql_id() {
# appropriate function definition goes here...
}
for ((ver=db_ver+1; ver<=lt_ver; ver++)); do
if echo "UPDATE client SET current_db_vers='${ver}' WHERE client_name='${client}'" | mysql_id; then
echo "Database upgraded.."
else
echo "Failed to upgrade.."
exit 1
fi
done
... but I'm not sure I understand what it's supposed to do. It seems to be updating current_db_vers one number at a time until it reaches $ver_lt... but why not set it directly to $ver_lt in a single UPDATE?
try something like :
done <<< "${UP_VER}"
I'm trying to write a wrapper for qrsh, the Oracle Grid Engine equivalent to rsh, and am having trouble identifying the command given to it. Consider the following example:
qrsh -cwd -V -now n -b y -N cvs -verbose -q some.q -p -98 cvs -Q log -N -S -d2012-04-09 14:02:08 GMT<2012-04-11 21:53:41 GMT -b
The command in this case starts from cvs. My wrapper needs to be general purpose so I can't look specifically for cvs. Any ideas on how to identify it? One thought is to look for executable commands starting from the end backwards, which will work in this case but won't be robust as "cvs" could appear in an option to itself. The only robust option that I can come up with is to fully implement the qrsh option parser but I'm not thrilled about it since it will need to be updated with qrsh updates and is complicated.
One option is to set QRSH_WRAPPER to echo and run qrsh once. However, this then requires two jobs to be issued instead of one, adding latency and wasting a slot.
I'm using Mercurial (specifically TortoiseHg on Windows) to do version control of VBA code. Anybody who's tried this knows that VBA changes the case of every variable throughout a project whenever any declaration of that variable is changed anywhere in the project (regardless of scope). It makes version control a nightmare.
I would like to ignore case changes in my source code when performing diffs. What is the easiest way to do this? (some option for diff that I'm missing, an external diff utility, something else?)
NOTE: I am not talking about dealing with 'case-insensitive filenames' (yes, I'm talking to you Google...)
You can do that when diffing for your on-screen consumption using the ExtDiff Extension.
[extensions]
hgext.extdiff =
[extdiff]
# add new command that runs GNU diff(1) in case-insensitive mode
cmd.mydiff = diff
opts.mydiff = -i
Then you'd run hg mydiff from the command line. That, of course, requires you have a diff binary installed be it gnu's or other.
However, that's not going to be as helpful as you might like because internally, of course, Mercurial can't ignore case -- it's taking the cryptographic hash of the file contents, and those don't allow for wiggle room. So if you get this set up you'll do hg mydiff, and see no changes, and then do hg commit and see changes all over the place.
So you can make this work on-screen, but not fundamentally.
One option would be to find a visual basic code-cleaner, similar to indent for C-like languages, that normalizes variable case and run that in a mercurial commit hook. Then at least all the code going into source control will be consistent and you can diff across revisions accurately.
If you are okay with having your code in all lower-case, say, then you could employ the encode/decode hooks for this. It would work like this:
[encode]
*.vba = tr A-Z a-z
This will encode the file content in lower-case whenever you do a commit. The diffs are also computed based on the encoded (repository) version of the files.
Consider a file that contains
hello
Changing it in your working copy to
Hello World
will give a diff of
% hg diff
diff --git a/a.txt b/a.txt
--- a/a.txt
+++ b/a.txt
## -1,1 +1,1 ##
-hello
+hello world
Notice how the capital "H" and "W" has been ignored.
I don't really know anything about VBA code, so I'm not 100% sure this solution works for you. But I hope it can be a starting point.
One drawback is that you'll need to set this encode rule for all your repositories. The reposettings extension can help you here.
Here's the solution I have settled on. It is far from ideal, but better than the other alternatives I've considered.
I created an Autohotkey script that does the following:
reverts MS Access files in a repository with detected changes (to .orig files)
reads in the .orig file (the one with the changes)
reads in the existing file (the one already in the repository)
converts the text of both files to lower case
compares the lower case contents of the files
if the files still differ, the .orig file is restored so it may be committed to the repository
if the files are the same (i.e., they differ only in case, the .orig file is deleted because we don't care about those changes)
For files that have actual changes that we care about, I still see the case changes that were made as well. If that results in a lot of noise, I open the file in a comparison tool that allows case-insensitive compares (e.g., kdiff).
It's not a perfect solution, but it removes about 90% of the frustration for me.
Here's my script. Note that the script includes another Autohotkey script, ConsoleApp.ahk, which provides a function named, ConsoleApp_RunWait(). This is a 3rd party script that no longer works very well with 64-bit AHK, so I'm not including it as part of my answer. Any AHK function that executes a command line and returns the output as a string will suffice.
; This script checks an MS Access source directory and reverts all files whose only modifications are to the
; case of the characters within the file.
#Include %A_ScriptDir%\ConsoleApp.ahk
#NoEnv ; Recommended for performance and compatibility with future AutoHotkey releases.
SendMode Input ; Recommended for new scripts due to its superior speed and reliability.
SetWorkingDir %A_ScriptDir% ; Ensures a consistent starting directory.
; Allow for custom path to hg (support for moving to TortoiseHg 2.0)
IniRead hg, %A_ScriptDir%\LocalSettings\Settings.cfg, TortoiseHg, hg_path, hg
if 0 < 1 ; The left side of a non-expression if-statement is always the name of a variable.
{
MsgBox Usage:`n`HgIgnoreCase DirectoryWithFilesToScrub
ExitApp
}
SrcDir = %1%
StringReplace SrcDir, SrcDir, ", , All
StringRight test, SrcDir, 1 ; add trailing slash if necessary
ifnotequal test, \
SrcDir = %SrcDir%\
RestoreOriginals(SrcDir)
RevertCaseChangeModifiedFiles(SrcDir)
RevertCaseChangeModifiedFiles(SrcDir) {
global hg
includes = -I "*.form" -I "*.bas" -I "*.report" -I "*.table"
cmdline = %hg% revert --all %includes%
;Don't revert items that have been removed completely
Loop 3
{
Result := ConsoleApp_RunWait(hg . " status -nrd " . includes, SrcDir)
If (Result)
Break
}
Loop parse, Result, `n, `r
{
if (A_LoopField)
cmdline = %cmdline% -X "%A_LoopField%"
}
Result =
;msgbox %cmdline%
;revert all modified forms, reports, and code modules
Loop 3
{
Result := ConsoleApp_RunWait(cmdline, SrcDir)
If (Result)
Break
}
;MsgBox %Result%
Loop parse, Result, `n, `r
{
StringLeft FileStatus, A_LoopField, 9
If (FileStatus = "reverting")
{
StringMid FName, A_LoopField, 11
FullPath = %SrcDir%%FName%
ToolTip Checking %FullPath%
RestoreIfNotEqual(FullPath, FullPath . ".orig")
}
}
ToolTip
}
RestoreIfNotEqual(FName, FNameOrig) {
FileRead File1, %FName%
FileRead File2, %FNameOrig%
StringLower File1, File1
StringLower File2, File2
;MsgBox %FName%`n%FNameOrig%
If (File1 = File2)
FileDelete %FNameOrig%
Else
FileMove %FNameOrig%, %FName%, 1
}
RestoreOriginals(SrcDir) {
Loop %SrcDir%*.orig
{
;MsgBox %A_LoopFileLongPath%`n%NewName%
NewName := SubStr(A_LoopFileLongPath, 1, -5)
FileMove %A_LoopFileLongPath%, %NewName%, 1
}
while FileExist(SrcDir . "*.orig")
Sleep 10
}
So the utility Diff works just like I want for 2 files, but I have a project that requires comparisons with more than 2 files at a time, maybe up to 10 at a time. This requires having all those files side by side to each other as well. My research has not really turned up anything, vimdiff seems to be the best so far with the ability to compare 4 at a time.
My question: Is there any utility to compare more than 2 files at a time, or a way to hack diff/vimdiff so it can do multiple comparisons? The files I will be comparing are relatively short so it should not be too slow.
Displaying 10 files side-by-side and highlighting differences can be easily done with Diffuse. Simply specify all files on the command line like this:
diffuse 1.txt 2.txt 3.txt 4.txt 5.txt 6.txt 7.txt 8.txt 9.txt 10.txt
Vim can already do this:
vim -d file1 file2 file3
But you're normally limited to 4 files. You can change that by modifying a single line in Vim's source, however. The constant DB_COUNT defines the maximum number of diffed files, and it's defined towards the top of diff.c in versions 6.x and earlier, or about two thirds of the way down structs.h in versions 7.0 and up.
diff has built-in option --from-file and --to-file, which compares one operand to all others.
--from-file=FILE1
Compare FILE1 to all operands. FILE1 can be a directory.
--to-file=FILE2
Compare all operands to FILE2. FILE2 can be a directory.
Note: argument name --to-file is optional.
e.g.
# this will compare foo with bar, then foo with baz .html files
$ diff --from-file foo.html bar.html baz.html
# this will compare src/base-main.js with all .js files in git repo,
# that has 'main' in their filename or path
$ git ls-files :/*main*.js | xargs diff -u --from-file src/base-main.js
Checkout "Beyond Compare": http://www.scootersoftware.com/
It lets you compare entire directories of files, and it looks like it runs on Linux too.
if your running multiple diff's based off one file you could probably try writing a script that has a for loop to run through each directory and run the diff. Although it wouldn't be side by side you could at least compare them quickly. hope that helped.
Not answering the main question, but here's something similar to what Benjamin Neil has suggested but diffing all files:
Store the filenames in an array, then loop over the combinations of size two and diff (or do whatever you want).
files=($(ls -d /path/of/files/some-prefix.*)) # Array of files to compare
max=${#files[#]} # Take the length of that array
for ((idxA=0; idxA<max; idxA++)); do # iterate idxA from 0 to length
for ((idxB=idxA + 1; idxB<max; idxB++)); do # iterate idxB + 1 from idxA to length
echo "A: ${files[$idxA]}; B: ${files[$idxB]}" # Do whatever you're here for.
done
done
Derived from #charles-duffy's answer: https://stackoverflow.com/a/46719215/1160428
There is a simple an good way to do this = GREP.
Depending on the size of the text you can copy and paste it, or you can redirect the input of the file to the grep command. If you make a grep -vir /path to make a reverse search or a grep -ir /path. This is my way for certification exams.