me@cbnewsh.att.com (william.j.bruncati) (01/19/91)
I am having a problem with an awk program. What I'm trying to do is have an array element match on a pattern in the first field. I can match on the fixed string but not the pattern. Can anyone help? This works. if (myarray[i] == $1 ) print $0 This doesn't work. It won't give me a match although there is one. if (myarray[i] ~ /$1/ ) print $0 Also, while I'm posting, could someone tell me if it's possible to have nested case statements in shell? Thanks in advance, Bill Bruncati
bob@wyse.wyse.com (Bob McGowen x4312 dept208) (01/20/91)
In article <1991Jan18.164243.11804@cbnewsh.att.com> me@cbnewsh.att.com (william.j.bruncati) writes: >I am having a problem with an awk program. >What I'm trying to do is have an array element >match on a pattern in the first field. >I can match on the fixed string >but not the pattern. Can anyone help? > >This works. > if (myarray[i] == $1 ) > print $0 > >This doesn't work. It won't give me a match although there is one. > if (myarray[i] ~ /$1/ ) > print $0 I believe this is because you are using "old" awk, which did not allow substitution into patterns, as with your "/$1/". Check to see if you have executables named "oawk" and "nawk". If so, "oawk" will most likely be linked to "awk", so you will want to change the command to "nawk". >Also, while I'm posting, could someone tell me if it's possible >to have nested case statements in shell? Yes, assuming you use sh.I do not know about csh. I have on occasion used the following to step through all arguments looking for options and then checking the options to see if they are legal ones: for arg in $* # assume no args will have white space do case $arg in -*) # this is an option case $arg in -h) ;; -p) ;; -x) ;; -*) ;; esac *) # this is not an option item="$item $arg" esac done > Thanks in advance, > Bill Bruncati I hope this is useful. Bob McGowan (standard disclaimer, these are my own ...) Product Support, Wyse Technology, San Jose, CA ..!uunet!wyse!bob bob@wyse.com
tchrist@convex.COM (Tom Christiansen) (01/20/91)
From the keyboard of bob@wyse.UUCP (Bob McGowen x4312 dept208):
:In article <1991Jan18.164243.11804@cbnewsh.att.com> me@cbnewsh.att.com (william.j.bruncati) writes:
:>This doesn't work. It won't give me a match although there is one.
:> if (myarray[i] ~ /$1/ )
:> print $0
:
: I believe this is because you are using "old" awk, which did not
: allow substitution into patterns, as with your "/$1/". Check to
: see if you have executables named "oawk" and "nawk". If so, "oawk"
: will most likely be linked to "awk", so you will want to change
: the command to "nawk".
:
And if like so many all you have is the old awk, get gawk, which is free.
You can also get perl, is a proper superset of all the awks (it comes
with awk-to-perl and sed-to-perl translators) and is also free.
--tom
--
"Hey, did you hear Stallman has replaced /vmunix with /vmunix.el? Now
he can finally have the whole O/S built-in to his editor like he
always wanted!" --me (Tom Christiansen <tchrist@convex.com>)jay@silence.princeton.nj.us (Jay Plett) (01/21/91)
In article <1991Jan20.062150.24582@convex.com>, tchrist@convex.COM (Tom Christiansen) writes: - From the keyboard of bob@wyse.UUCP (Bob McGowen x4312 dept208): - :In article <1991Jan18.164243.11804@cbnewsh.att.com> me@cbnewsh.att.com (william.j.bruncati) writes: - :>This doesn't work. It won't give me a match although there is one. - :> if (myarray[i] ~ /$1/ ) - :> print $0 - : - : I believe this is because you are using "old" awk, which did not - : allow substitution into patterns, as with your "/$1/". - - And if like so many all you have is the old awk, get gawk, which is free. Either nawk or gawk are worth having. But I don't believe that either of them will solve the stated problem. I've never been able to find a way to use a variable on the right-hand side of a ~ expression with any of the incarnations of awk. Have I missed something? ...jay
tchrist@convex.COM (Tom Christiansen) (01/21/91)
From the keyboard of jay@silence.princeton.nj.us (Jay Plett):
:I've never been able to find a way to use a variable on the right-hand
:side of a ~ expression with any of the incarnations of awk. Have I
:missed something?
Hmm, now that you mention it, there's no way for awk to distinguish
if (myarray[i] ~ /foo/)
is the literal or the variable foo. I guess that's the price you pay for
not having variable markers as you do in the shell or perl. Certainly in
perl there's a big difference between
if ($myarray[$i] =~ /foo/) # can't use ~ -- that's bitwise negation, per C
and
if ($myarray[$i] =~ /$foo/)
I shall say no more. :-)
--tom
--
"Hey, did you hear Stallman has replaced /vmunix with /vmunix.el? Now
he can finally have the whole O/S built-in to his editor like he
always wanted!" --me (Tom Christiansen <tchrist@convex.com>)dag@fciva.FRANKCAP.COM (Daniel A. Graifer) (01/21/91)
In article <1991Jan20.232154.29651@convex.com> tchrist@convex.COM (Tom Christiansen) writes: >From the keyboard of jay@silence.princeton.nj.us (Jay Plett): >:I've never been able to find a way to use a variable on the right-hand >:side of a ~ expression with any of the incarnations of awk. Have I >:missed something? > >Hmm, now that you mention it, there's no way for awk to distinguish > > if (myarray[i] ~ /foo/) > >is the literal or the variable foo. $ nawk 'BEGIN{ x="aw fubar anyways" foo="bar" if ( x ~ foo ) print "Yep" else print "Nope" }' Yep $ nawk 'BEGIN{ x="aw fubar anyways" foo="b.r" if ( x ~ foo ) print "Yep" else print "Nope" }' Yep 'nuff said Dan -- Daniel A. Graifer Coastal Capital Funding Corp. Sr. Vice President, Financial Systems 7900 Westpark Dr. Suite A-130 (703)821-3244 McLean, VA 22102 uunet!fciva!dag fciva.FRANKCAP.COM!dag@uunet.uu.net
]) (01/22/91)
In article <681@silence.princeton.nj.us> jay@silence.princeton.nj.us (Jay Plett) writes: >In article <1991Jan20.062150.24582@convex.com>, tchrist@convex.COM (Tom Christiansen) writes: >- From the keyboard of bob@wyse.UUCP (Bob McGowen x4312 dept208): >- :In article <1991Jan18.164243.11804@cbnewsh.att.com> me@cbnewsh.att.com (william.j.bruncati) writes: >- :>This doesn't work. It won't give me a match although there is one. >- :> if (myarray[i] ~ /$1/ ) >- :> print $0 >- : >- : I believe this is because you are using "old" awk, which did not >- : allow substitution into patterns, as with your "/$1/". >- >- And if like so many all you have is the old awk, get gawk, which is free. > >Either nawk or gawk are worth having. But I don't believe that either >of them will solve the stated problem. > >I've never been able to find a way to use a variable on the right-hand >side of a ~ expression with any of the incarnations of awk. Have I >missed something? Well, in nawk, this works... if ( match(myarray[i], $1) > 0 ) { print "record", NR, "matched somewhere on entry", i print $0 } if ( match(myarray[i], $1) == 1 ) { print "record", NR, "matched start of array item", i print $0 } In a related vein, I often do something like this... BEGIN { keywords = " first second third " ebadkey = "invalid keyword '%s' on record %d\n" } # # Handle a valid keyword # $1 == "key" && match(keywords, " " $2 " " { print "I'd do something with the key, " $2 ", here." next } # # Bad keyword record! # $1 == "key" { printf(ebadkey, $2, NR) | "/bin/cat 1>&2" errorcount++ next } # # Report error count # END { if ( errorcount > 0 ) print errorcount, "errors found" | "/bin/cat 1>&2" } ...Kris -- Kristopher Stephens, | (408-746-6047) | krs@uts.amdahl.com | KC6DFS Amdahl Corporation | | | [The opinions expressed above are mine, solely, and do not ] [necessarily reflect the opinions or policies of Amdahl Corp. ]
tchrist@convex.COM (Tom Christiansen) (01/22/91)
From the keyboard of dag@fciva.UUCP (Daniel A. Graifer):
:In article <1991Jan20.232154.29651@convex.com> I said:
:>:I've never been able to find a way to use a variable on the right-hand
:>:side of a ~ expression with any of the incarnations of awk. Have I
:>:missed something?
:>
:>Hmm, now that you mention it, there's no way for awk to distinguish
:>
:> if (myarray[i] ~ /foo/)
:>
:>is the literal or the variable foo.
:
:$ nawk 'BEGIN{
Ah, a _nawk solution. Shoulda known. :-) I had perl two years
before I got gawk, and the awk on my system is still the old one.
thanks,
-tom
--
"Hey, did you hear Stallman has replaced /vmunix with /vmunix.el? Now
he can finally have the whole O/S built-in to his editor like he
always wanted!" --me (Tom Christiansen <tchrist@convex.com>)haozhou@acsu.buffalo.edu (Hao Zhou) (02/28/91)
I am using awk to print some selected lines from a text file. What I
want to to is to hold off the current line until next line comes in
and a certain condition is satisfied before printing both lines. So I
need to store the current line in some variable as follows:
prev = 'initialization'
awk '{{if (condition) \
printf("%s \n %s \n", $prev, $0)}
{prev=$0}}'
However the variable prev doesn't store the previous line. Instead the
printf prints out twice the current line. What am I doing wrong?
Thanks for any help on this problem.
Hao
--
Internet:haozhou@acsu.buffalo.edu BITNET:haozhou%acsu.buffalo.edu@UBVM.BITNET
UUCP: rutgers!ub!haozhoujik@athena.mit.edu (Jonathan I. Kamens) (02/28/91)
In article <62322@eerie.acsu.Buffalo.EDU>, haozhou@acsu.buffalo.edu (Hao Zhou) writes: |> prev = 'initialization' |> awk '{{if (condition) \ |> printf("%s \n %s \n", $prev, $0)} |> {prev=$0}}' |> |> However the variable prev doesn't store the previous line. Instead the |> printf prints out twice the current line. What am I doing wrong? First of all, what is the first line of the script, prev = 'initialization' supposed to be doing? Since that command appears outside of the awk command, it sets a shell variable, not an awk variable! Second, variables in awk are not referred to using '$' -- only line fields are. So the "$prev" in the printf above should just be "prev". It's likely that in "$prev", prev is getting interpreted as a number, and since it's a string awk ends up thinking that it's equal to 0, and therefore uses $0, which is why the same line prints twice. Third, where's the condition? It looks to me like you tried to cut down the code you're actually using in order to post a short example to the net, and you managed to butcher it up enough in the process that it's not easy for us to help you. But I'll try: awk 'BEGIN { prev = "" } { if (condition) prinf("%s\n%s\n", prev, $0) } { prev = $0 }' -- Jonathan Kamens USnail: MIT Project Athena 11 Ashford Terrace jik@Athena.MIT.EDU Allston, MA 02134 Office: 617-253-8085 Home: 617-782-0710
art@pilikia.pegasus.com (Art Neilson) (02/28/91)
In article <62322@eerie.acsu.Buffalo.EDU> haozhou@acsu.buffalo.edu (Hao Zhou) writes: >I am using awk to print some selected lines from a text file. What I >want to to is to hold off the current line until next line comes in >and a certain condition is satisfied before printing both lines. So I >need to store the current line in some variable as follows: > > prev = 'initialization' > awk '{{if (condition) \ > printf("%s \n %s \n", $prev, $0)} > {prev=$0}}' > >However the variable prev doesn't store the previous line. Instead the >printf prints out twice the current line. What am I doing wrong? > >Thanks for any help on this problem. > > > Hao > >-- >Internet:haozhou@acsu.buffalo.edu BITNET:haozhou%acsu.buffalo.edu@UBVM.BITNET >UUCP: rutgers!ub!haozhou All your curly braces are quite confusing. This looks like what you're trying to do. awk ' BEGIN { prev = 'initialization' } { if (condition) printf("%s \n %s \n", prev, $0) prev = $0 }' -- Arthur W. Neilson III | INET: art@pilikia.pegasus.com Bank of Hawaii Tech Support | UUCP: uunet!ucsd!nosc!pegasus!pilikia!art
mjm@eleazar.dartmouth.edu (Andy Behrens) (03/01/91)
haozhou@acsu.buffalo.edu (Hao Zhou) writes: > I am using awk to print some selected lines from a text file. What I > want to to is to hold off the current line until next line comes in > and a certain condition is satisfied before printing both lines. > > awk '{{if (condition) \ > printf("%s \n %s \n", $prev, $0)} > {prev=$0}}' > >However the variable prev doesn't store the previous line. Instead the >printf prints out twice the current line. What am I doing wrong? You should write 'prev' instead of '$prev'. Awk variables (unlike shell variables) are written without a dollar sign. The awk statements n="3" print $n # or print $(n) will print the third field of the input line. -- If you've got a hammer, If the only tool you have find a nail. is a hammer, you tend to see (George Bush, January 29, 1991) every problem as a nail. (Abraham Maslow) +-------------------+ | Andy Behrens | or: andyb%coat.com@dartmouth.edu | andyb@coat.com | bitnet: andyb%coat.com@dartcms1 +-------------------+ uucp: {uunet,rutgers}!dartvax!coat.com!andyb RFD #1, Box 116, East Thetford, Vt. 05043 (802) 649-1258 Burlington Coat, HC 61 Box 1B, Lebanon, N.H. 03766 (603) 448-5000