We are currently using sed to filter output of regression runs. Sometimes we have a filter that looks like this:
/copyright/,/end copyright/d
If that end copyright is ever missing, the rest of the file is deleted. I'm wondering if there's some way to generate an error for this? awk would also be okay to use. I don't really want to add code that reads the file line by line and issues an error if it hits EOF.
here's a string
copyright
2016 jan 15
end copyright
date 2016 jan 5 time 15:36
last one
I'd like to get an error if end copyright is missing. The real filter also would replace the date line with DATE, so it's more that just ripping out the copyright.
You can persuade sed to generate an error if you reach end of input (i.e. see address $) between your start and end, but it won't be a very helpful message:
/copyright/,/end copyright/{
$s//\1/ # here
d
}
This will error if end copyright is missing or on the last line, with an exit status of 1 and the helpful message:
sed: -e expression #1, char 0: invalid reference \1 on `s' command's RHS
If you're using this in a makefile, you might want to echo a helpful message first, or (better) to wrap this in something that catches the error and produces a more useful one.
I tested this with GNU sed; though if you are using GNU sed, you could more easily use its useful extension:
q [EXIT-CODE]
This command only accepts a single address.
Exit 'sed' without processing any more commands or input. Note
that the current pattern space is printed if auto-print is not
disabled with the -n options. The ability to return an exit code
from the 'sed' script is a GNU 'sed' extension.
Q [EXIT-CODE]
This command only accepts a single address.
This command is the same as 'q', but will not print the contents of
pattern space. Like 'q', it provides the ability to return an exit
code to the caller.
So you could simply write
/copyright/,/end copyright/{
$Q 42
d
}
Never use range expressions /start/,/end/ as they make trivial code very slightly briefer but require a complete rewrite or duplicate conditions when you have the tiniest requirements change. Always use a flag instead. Note that since sed doesn't support variables, it doesn't support flag variables, and so you shouldn't be using sed you should be using awk instead.
In this case your original code would be:
awk '/copyright/{f=1} !f; /end copyright/{f=0}' file
And your modified code would be:
awk '/copyright/{f=1} !f; /end copyright/{f=0} END{if (f) print "Missing end copyright"}' file
The above is obviously untested since you didn't provide any sample input/output we could test a potential solution against.
With sed you can build a loop:
sed -e '/copyright/{:a;/end copyright/d;N;ba;};' file
:a defines the label "a"
/copyright end/d deletes the pattern space, only when "end copyright" matches
N appends the next line to the pattern space
ba jumps to the label "a"
Note that d ends the loop.
In this way you can avoid to delete the text until the end.
If you don't want the text to be displayed at all and prefer an error message when a "copyright" block stays unclosed, you obviously need to wait the end of the file. You can do it with sed too storing all the lines in the buffer space until the end:
sed -n -e '/copyright/{:a;/end copyright/d;${c\ERROR MESSAGE
;};N;ba;};H;${g;p};' file
H appends the current line to the buffer space
g put the content of the buffer space to the pattern space
The file content is only displayed once the last line reached with ${g;p} otherwise when the closing "end copyright" is missing, the current line is changed in the error message with ${c\ERROR MESSAGE\n;} inside the loop.
This way you can test what returns sed before redirecting it to whatever you want.
I want to save the output of a program to a variable.
I use the following approach ,but fail.
$ PIPE RUN TEST | DEFINE/JOB VALUE #SYS$PIPE
$ x = f$logical("VALUE")
I got an error:%DCL-W-MAXPARM, too many parameters - reenter command with fewer parameters
\WORLD\
reference :
How to assign the output of a program to a variable in a DCL com script on VMS?
The usual way to do this is to write the output to a file and read from the file and put that into a DCL symbol (or logical). Although not obvious, you can do this with the PIPE command was well:
$ pipe r 2words
hello world
$ pipe r 2words |(read sys$pipe line ; line=""""+line+"""" ; def/job value &line )
$ sh log value
"VALUE" = "hello world" (LNM$JOB_85AB4440)
$
IF you are able to change the program, add some code to it to write the required values into symbols or logicals (see LIB$ routines)
If you can modify the program, using LIB$SET_SYMBOL in the program defines a DCL symbol (what you are calling a variable) for DCL. That's the cleanest way to do this. If it really needs to be a logical, then there are system calls that define logicals.
I have a problem with ksh in that a while loop is failing to obey the "while" condition. I should add now that this is ksh88 on my client's Solaris box. (That's a separate problem that can't be addressed in this forum. ;) I have seen Lance's question and some similar but none that I have found seem to address this. (Disclaimer: NO I haven't looked at every ksh question in this forum)
Here's a very cut down piece of code that replicates the problem:
1 #!/usr/bin/ksh
2 #
3 go=1
4 set -x
5 tail -0f loop-test.txt | while [[ $go -eq 1 ]]
6 do
7 read lbuff
8 set $lbuff
9 nwords=$#
10 printf "Line has %d words <%s>\n" $nwords "${lbuff}"
11 if [[ "${lbuff}" = "0" ]]
12 then
13 printf "Line consists of %s; time to absquatulate\n" $lbuff
14 go=0 # Violate the WHILE condition to get out of loop
15 fi
16 done
17 printf "\nLooks like I've fallen out of the loop\n"
18 exit 0
The way I test this is:
Run loop-test.sh in background mode
In a different window I run commands like "echo some nonsense >>loop_test.txt" (w/o the quotes, of course)
When I wish to exit, I type "echo 0 >>loop-test.txt"
What happens? It indeed sets go=0 and displays the line:
Line consists of 0; time to absquatulate
but does not exit the loop. To break out I append one more line to the txt file. The loop does NOT process that line and just falls out of the loop, issuing that "fallen out" message before exiting.
What's going on with this? I don't want to use "break" because in the actual script, the loop is monitoring the log of a database engine and the flag is set when it sees messages that the engine is shutting down. The actual script must still process those final lines before exiting.
Open to ideas, anyone?
Thanks much!
-- J.
OK, that flopped pretty quick. After reading a few other posts, I found an answer given by dogbane that sidesteps my entire pipe-to-while scheme. His is the second answer to a question (from 2013) where I see neeraj is using the same scheme I'm using.
What was wrong? The pipe-to-while has always worked for input that will end, like a file or a command with a distinct end to its output. However, from a tail command, there is no distinct EOF. Hence, the while-in-a-subshell doesn't know when to terminate.
Dogbane's solution: Don't use a pipe. Applying his logic to my situation, the basic loop is:
while read line
do
# put loop body here
done < <(tail -0f ${logfile})
No subshell, no problem.
Caveat about that syntax: There must be a space between the two < operators; otherwise it looks like a HEREIS document with bad syntax.
Er, one more catch: The syntax did not work in ksh, not even in the mksh (under cygwin) which emulates ksh93. But it did work in bash. So my boss is gonna have a good laugh at me, 'cause he knows I dislike bash.
So thanks MUCH, dogbane.
-- J
After articulating the problem and sleeping on it, the reason for the described behavior came to me: After setting go=0, the control flow of the loop still depends on another line of data coming in from STDIN via that pipe.
And now that I have realized the cause of the weirdness, I can speculate on an alternative way of reading from the stream. For the moment I am thinking of the following solution:
Open the input file as STDIN (Need to research the exec syntax for that)
When the condition occurs, close STDIN (Again, need to research the syntax for that)
It should then be safe to use the more intuitive:while read lbuffat the top of the loop.
I'll test this out today and post the result. I'd hope someone else benefit from the method (if it works).
I'm using
while( (getline line < "filename") > 0 )
within my BEGIN statement, but this while loop only seems to read the last line of the file instead of each line. I think it may be a newline character problem, but really I don't know. Any ideas?
I'm trying to read the data in from a file other than the main input file.
The same syntax actually works for one file, but not another, and the only difference I see is that the one for which it DOES work has "^M" at the end of each line when I look at it in Vim, and the one for which it DOESN'T work doesn't have ^M. But this seems like an odd problem to be having on my (UNIX based) Mac.
I wish I understood what was going with getline a lot better than I do.
You would have to specify RS to something more vague.
Here is a ugly hack to get things working
RS="[\x0d\x0a\x0d]"
Now, this may require some explanation.
Diffrent systems use difrent ways to handle change of line.
Read http://en.wikipedia.org/wiki/Carriage_return and http://en.wikipedia.org/wiki/Newline if you are
interested in it.
Normally awk hadles this gracefully, but it appears that in your enviroment, some files are being naughty.
0x0d or 0x0a or 0x0d 0x0a (CR+LF) should be there, but not mixed.
So lets try a example of a mixed data stream
$ echo -e "foo\x0d\x0abar\x0d\x0adoe\x0arar\x0azoe\x0dqwe\x0dtry" |awk 'BEGIN{while((getline r )>0){print "r=["r"]";}}'
Result:
r=[foo]
r=[bar]
r=[doe]
r=[rar]
try]oe
We can see that the last lines are lost.
Now using the ugly hack to RS
$ echo -e "foo\x0d\x0abar\x0d\x0adoe\x0arar\x0azoe\x0dqwe\x0dtry" |awk 'BEGIN{RS="[\x0d\x0a\x0d]";while((getline r )>0){print "r=["r"]";}}'
Result:
r=[foo]
r=[bar]
r=[doe]
r=[rar]
r=[zoe]
r=[qwe]
r=[try]
We can see every line is obtained, reguardless of the 0x0d 0x0a junk :-)
Maybe you should preprocess your input file with for example dos2unix (http://sourceforge.net/projects/dos2unix/) utility?
It's the first great virtue of programmers. All of us have, at one time or another automated a task with a bit of throw-away code. Sometimes it takes a couple seconds tapping out a one-liner, sometimes we spend an exorbitant amount of time automating away a two-second task and then never use it again.
What tiny hack have you found useful enough to reuse? To make go so far as to make an alias for?
Note: before answering, please check to make sure it's not already on favourite command-line tricks using BASH or perl/ruby one-liner questions.
i found this on dotfiles.org just today. it's very simple, but clever. i felt stupid for not having thought of it myself.
###
### Handy Extract Program
###
extract () {
if [ -f $1 ] ; then
case $1 in
*.tar.bz2) tar xvjf $1 ;;
*.tar.gz) tar xvzf $1 ;;
*.bz2) bunzip2 $1 ;;
*.rar) unrar x $1 ;;
*.gz) gunzip $1 ;;
*.tar) tar xvf $1 ;;
*.tbz2) tar xvjf $1 ;;
*.tgz) tar xvzf $1 ;;
*.zip) unzip $1 ;;
*.Z) uncompress $1 ;;
*.7z) 7z x $1 ;;
*) echo "'$1' cannot be extracted via >extract<" ;;
esac
else
echo "'$1' is not a valid file"
fi
}
Here's a filter that puts commas in the middle of any large numbers in standard input.
$ cat ~/bin/comma
#!/usr/bin/perl -p
s/(\d{4,})/commify($1)/ge;
sub commify {
local $_ = shift;
1 while s/^([ -+]?\d+)(\d{3})/$1,$2/;
return $_;
}
I usually wind up using it for long output lists of big numbers, and I tire of counting decimal places. Now instead of seeing
-rw-r--r-- 1 alester alester 2244487404 Oct 6 15:38 listdetail.sql
I can run that as ls -l | comma and see
-rw-r--r-- 1 alester alester 2,244,487,404 Oct 6 15:38 listdetail.sql
This script saved my career!
Quite a few years ago, i was working remotely on a client database. I updated a shipment to change its status. But I forgot the where clause.
I'll never forget the feeling in the pit of my stomach when I saw (6834 rows affected). I basically spent the entire night going through event logs and figuring out the proper status on all those shipments. Crap!
So I wrote a script (originally in awk) that would start a transaction for any updates, and check the rows affected before committing. This prevented any surprises.
So now I never do updates from command line without going through a script like this. Here it is (now in Python):
import sys
import subprocess as sp
pgm = "isql"
if len(sys.argv) == 1:
print "Usage: \nsql sql-string [rows-affected]"
sys.exit()
sql_str = sys.argv[1].upper()
max_rows_affected = 3
if len(sys.argv) > 2:
max_rows_affected = int(sys.argv[2])
if sql_str.startswith("UPDATE"):
sql_str = "BEGIN TRANSACTION\\n" + sql_str
p1 = sp.Popen([pgm, sql_str],stdout=sp.PIPE,
shell=True)
(stdout, stderr) = p1.communicate()
print stdout
# example -> (33 rows affected)
affected = stdout.splitlines()[-1]
affected = affected.split()[0].lstrip('(')
num_affected = int(affected)
if num_affected > max_rows_affected:
print "WARNING! ", num_affected,"rows were affected, rolling back..."
sql_str = "ROLLBACK TRANSACTION"
ret_code = sp.call([pgm, sql_str], shell=True)
else:
sql_str = "COMMIT TRANSACTION"
ret_code = sp.call([pgm, sql_str], shell=True)
else:
ret_code = sp.call([pgm, sql_str], shell=True)
I use this script under assorted linuxes to check whether a directory copy between machines (or to CD/DVD) worked or whether copying (e.g. ext3 utf8 filenames -> fusebl
k) has mangled special characters in the filenames.
#!/bin/bash
## dsum Do checksums recursively over a directory.
## Typical usage: dsum <directory> > outfile
export LC_ALL=C # Optional - use sort order across different locales
if [ $# != 1 ]; then echo "Usage: ${0/*\//} <directory>" 1>&2; exit; fi
cd $1 1>&2 || exit
#findargs=-follow # Uncomment to follow symbolic links
find . $findargs -type f | sort | xargs -d'\n' cksum
Sorry, don't have the exact code handy, but I coded a regular expression for searching source code in VS.Net that allowed me to search anything not in comments. It came in very useful in a particular project I was working on, where people insisted that commenting out code was good practice, in case you wanted to go back and see what the code used to do.
I have two ruby scripts that I modify regularly to download all of various webcomics. Extremely handy! Note: They require wget, so probably linux. Note2: read these before you try them, they need a little bit of modification for each site.
Date based downloader:
#!/usr/bin/ruby -w
Day = 60 * 60 * 24
Fromat = "hjlsdahjsd/comics/st%Y%m%d.gif"
t = Time.local(2005, 2, 5)
MWF = [1,3,5]
until t == Time.local(2007, 7, 9)
if MWF.include? t.wday
`wget #{t.strftime(Fromat)}`
sleep 3
end
t += Day
end
Or you can use the number based one:
#!/usr/bin/ruby -w
Fromat = "http://fdsafdsa/comics/%08d.gif"
1.upto(986) do |i|
`wget #{sprintf(Fromat, i)}`
sleep 1
end
Instead of having to repeatedly open files in SQL Query Analyser and run them, I found the syntax needed to make a batch file, and could then run 100 at once. Oh the sweet sweet joy! I've used this ever since.
isqlw -S servername -d dbname -E -i F:\blah\whatever.sql -o F:\results.txt
This goes back to my COBOL days but I had two generic COBOL programs, one batch and one online (mainframe folks will know what these are). They were shells of a program that could take any set of parameters and/or files and be run, batch or executed in an IMS test region. I had them set up so that depending on the parameters I could access files, databases(DB2 or IMS DB) and or just manipulate working storage or whatever.
It was great because I could test that date function without guessing or test why there was truncation or why there was a database ABEND. The programs grew in size as time went on to include all sorts of tests and become a staple of the development group. Everyone knew where the code resided and included them in their unit testing as well. Those programs got so large (most of the code were commented out tests) and it was all contributed by people through the years. They saved so much time and settled so many disagreements!
I coded a Perl script to map dependencies, without going into an endless loop, For a legacy C program I inherited .... that also had a diamond dependency problem.
I wrote small program that e-mailed me when I received e-mails from friends, on an rarely used e-mail account.
I wrote another small program that sent me text messages if my home IP changes.
To name a few.
Years ago I built a suite of applications on a custom web application platform in PERL.
One cool feature was to convert SQL query strings into human readable sentences that described what the results were.
The code was relatively short but the end effect was nice.
I've got a little app that you run and it dumps a GUID into the clipboard. You can run it /noui or not. With UI, its a single button that drops a new GUID every time you click it. Without it drops a new one and then exits.
I mostly use it from within VS. I have it as an external app and mapped to a shortcut. I'm writing an app that relies heavily on xaml and guids, so I always find I need to paste a new guid into xaml...
Any time I write a clever list comprehension or use of map/reduce in python. There was one like this:
if reduce(lambda x, c: locks[x] and c, locknames, True):
print "Sub-threads terminated!"
The reason I remember that is that I came up with it myself, then saw the exact same code on somebody else's website. Now-adays it'd probably be done like:
if all(map(lambda z: locks[z], locknames)):
print "ya trik"
I've got 20 or 30 of these things lying around because once I coded up the framework for my standard console app in windows I can pretty much drop in any logic I want, so I got a lot of these little things that solve specific problems.
I guess the ones I'm using a lot right now is a console app that takes stdin and colorizes the output based on xml profiles that match regular expressions to colors. I use it for watching my log files from builds. The other one is a command line launcher so I don't pollute my PATH env var and it would exceed the limit on some systems anyway, namely win2k.
I'm constantly connecting to various linux servers from my own desktop throughout my workday, so I created a few aliases that will launch an xterm on those machines and set the title, background color, and other tweaks:
alias x="xterm" # local
alias xd="ssh -Xf me#development_host xterm -bg aliceblue -ls -sb -bc -geometry 100x30 -title Development"
alias xp="ssh -Xf me#production_host xterm -bg thistle1 ..."
I have a bunch of servers I frequently connect to, as well, but they're all on my local network. This Ruby script prints out the command to create aliases for any machine with ssh open:
#!/usr/bin/env ruby
require 'rubygems'
require 'dnssd'
handle = DNSSD.browse('_ssh._tcp') do |reply|
print "alias #{reply.name}='ssh #{reply.name}.#{reply.domain}';"
end
sleep 1
handle.stop
Use it like this in your .bash_profile:
eval `ruby ~/.alias_shares`