Have a 40mb single line file where there is no fixed width or delimiting character. But each record starts with a P followed by either a P or S and then a number. So might be like:
PP5
-or-
PS5
Or PP0 , etc.
What's the best way to separate this out?
$ echo PP5xxxPS5yyyyPP0zzz | awk -F'P[PS][0-9]' -v OFS='\n' '{$1=$1}1'
xxx
yyyy
zzz
since starts with the delimiter there is a blank first line, which can be eliminated if important.
If you want to preserve the delimiters, perhaps easier with sed
$ echo PP5xxxPS5yyyyPP0zzz | sed 's/P[PS][0-9]/\n&/g'
PP5xxx
PS5yyyy
PP0zzz
Borrowing #karakfa's sample input, this might be what you want (using GNU awk for multi-char RS and RT):
$ echo 'PP5xxxPS5yyyyPP0zzz' | awk -v RS='P[PS][0-9]|\n' 'NR>1{print pRT $0} {pRT=RT}'
PP5xxx
PS5yyyy
PP0zzz
The differences between that gawk solution and the sed solution #karakfa suggested are:
The sed solution will print a blank line at the start of the output while the above won't, and
The sed solution will read the whole input line into memory at once while the above will only read one RS-separated block into memory at a time. That would only matter if your input was too huge to fit in memory all at once.
The sed script is portable to any version of sed that allows \n in the replacement text to mean "newline" and is easily modified to use an escaped literal newline in others while the above requires GNU awk.
the line begins with P then P/S then #. Where a line begins is where one ends so why not use a fixed RS instead of regex one. Maybe
{mawk/mawk2/gawk} 'BEGIN { FS = "^$" ; RS = "\nP" ;
} FNR==1 { sub(/^P/, "") } { print "P" $0 } '
Let RS take the P off, and pad it back in print. Either print+next or single sub() for 1st row case. I prefer a condition that only runs once for FNR==1 than the opposite requiring FNR > 1.
Yes last line technically won't get split by RS. And that's one of awk's known weaknesses - final line will print with ORS the same, with or without a RS at EOF.
I wrote it this way to allow for variants that don't have RT (basically everyone else). RT makes life easy.
I'm trying to find quoted strings in a file. Occasionally, those strings might have special characters including slashed quotes (e.g. \").
Using a zsh command, on macOS Catalina (gnu sed, not bsd; although awk, etc... is fine too), what's the most efficient way for me to cache those values in an array?
Sample Input:
a file that contains...
The "quick" "\(brown)" fox
jumps "over \n\"the $?#%\"" fence
Expected Output:
the array below...
echo -E - ${array[#]}
"quick" "\(brown)" "over \n\"the $?#%\""
EDIT
I'm willing to forgo the efficient part, and just focus on something that will work.
Also I’m not trying to handcuff anyone to awk or sed. The script needs to be able to run on a vanilla macOS system, any commands available there are fine.
EDIT
So here's where I'm currently at...
while read line; do
echo -E - $line | sed 's/\\*(/\\\(/g' | awk -F\" '{print $2}'
done < SampleInput
...which outputs:
quick
over n
At this point, I need two things to be fixed to print the values that I'd be storing in the array:
(1) I need to preserve the special characters.
(2) I need to keep more than just the second field. Thinking I need to count the quotes while ignoring the escaped quote, then print every other field.
From there, loading those printed fields into an array using xargs shouldn't be too hard to figure out.
Had some other similar questions recently, so I think it's possible to preserve the special characters; what will be ugly is skipping every other fields.
Eventually I'll get this, but I would appreciate the help from anyone who knows these commands better.
Thanks in advance.
Here is an attempt with awk but it needs more testing, I only tested for the sample input.
> cat test.awk
BEGIN { RS="\"" }
p { printf "%s", $0 }
($0 ~ /\\$/) { if (p) { printf "%s", "\"" }; next }
{ if (p) { p=0 } else { p=1; printf "\n" } }
p is the printing mode and RS is the double quote. We do not switch the printing mode if we find an escaping double quote, that means a record ending with backlash.
> cat file
The "quick" "\(brown)" fox
jumps "over \n\"the $?#%\"" fence
> awk -f test.awk file
quick
\(brown)
over \n\"the $?#%\"
This might work for you (GNU sed):
sed -E 's/^[^"]*"([^"\]*(\\.[^"\]*)*)" */\1\n/;/^[^\n]*\n/P;D' file > file1
The sed invocation whittles down each line in file, removing any non-words (strings not surrounded by double quotes) and places a newline after a recognised word. Thus each line of file1 will contain a double quoted word, less its double quotes.
N.B. The regexp ignores any character following a \
Can someone please explain to me how I can combine these piped awks to a single awk?
awk 'match($0, /(,|^)[^,]*shalvar[^,]*(,|$)/) {
print substr($0, RSTART, RLENGTH)}' file.txt |
awk 'gsub(",","")' | awk '{$1=$1};1'
I try this but it doesn't work:
awk 'match($0, /(,|^)[^,]*shalvar[^,]*(,|$)/) {
gsub(",","");$1=$1;print substr($0, RSTART, RLENGTH)}' file.txt
I understand that it shouldn't work because the characters are removed but the pointers don't change. How can I fix it now?
You need to wrap things the other way around. Collect the string you want to extract, then do the manipulations on the extracted value, just like your original script with multiple Awk scripts in a pipeline did.
awk 'match($0, /(,|^)[^,]*shalvar[^,]*(,|$)/) {
g=substr($0, RSTART, RLENGTH);
gsub(",","",g);
# $1=$1 is nice but we cannot use that here; here is a workaround
gsub(/^ *| *$/, "", g);
print g}' file.txt
The shortcut $1=$1 for trimming whitespace around a value works in an isolated Awk script if you are confident that there is only one field, but here, we don't necessarily have a single field (or do we?) so I use a more general solution to explicitly trim whitespace around the extracted string which also avoids relying on a well-known but still obscure side effect.
If shalvar is actually a variable you want to receive from the shell like $foo , try
awk -v field="$foo" 'match($0, "(^|,)[^,]*" field "[^,]*(,|$)") {
...
to interpolate the variable into a string which is then applied as a regular expression.
I have a case where I want to use input from a file as the format for printf() in awk. My formatting works when I set it in a string within the code, but it doesn't work when I load it from input.
Here's a tiny example of the problem:
$ # putting the format in a variable works just fine:
$ echo "" | awk -vs="hello:\t%s\n\tfoo" '{printf(s "bar\n", "world");}'
hello: world
foobar
$ # But getting the format from an input file does not.
$ echo "hello:\t%s\n\tfoo" | awk '{s=$0; printf(s "bar\n", "world");}'
hello:\tworld\n\tfoobar
$
So ... format substitutions work ("%s"), but not special characters like tab and newline. Any idea why this is happening? And is there a way to "do something" to input data to make it usable as a format string?
UPDATE #1:
As a further example, consider the following using bash heretext:
[me#here ~]$ awk -vs="hello: %s\nworld: %s\n" '{printf(s, "foo", "bar");}' <<<""
hello: foo
world: bar
[me#here ~]$ awk '{s=$0; printf(s, "foo", "bar");}' <<<"hello: %s\nworld: %s\n"
hello: foo\nworld: bar\n[me#here ~]$
As far as I can see, the same thing happens with multiple different awk interpreters, and I haven't been able to locate any documentation that explains why.
UPDATE #2:
The code I'm trying to replace currently looks something like this, with nested loops in shell. At present, awk is only being used for its printf, and could be replaced with a shell-based printf:
#!/bin/sh
while read -r fmtid fmt; do
while read cid name addy; do
awk -vfmt="$fmt" -vcid="$cid" -vname="$name" -vaddy="$addy" \
'BEGIN{printf(fmt,cid,name,addy)}' > /path/$fmtid/$cid
done < /path/to/sampledata
done < /path/to/fmtstrings
Example input would be:
## fmtstrings:
1 ID:%04d Name:%s\nAddress: %s\n\n
2 CustomerID:\t%-4d\t\tName: %s\n\t\t\t\tAddress: %s\n
3 Customer: %d / %s (%s)\n
## sampledata:
5 Companyname 123 Somewhere Street
12 Othercompany 234 Elsewhere
My hope was that I'd be able to construct something like this to do the entire thing with a single call to awk, instead of having nested loops in shell:
awk '
NR==FNR { fmts[$1]=$2; next; }
{
for(fmtid in fmts) {
outputfile=sprintf("/path/%d/%d", fmtid, custid);
printf(fmts[fmtid], $1, $2) > outputfile;
}
}
' /path/to/fmtstrings /path/to/sampledata
Obviously, this doesn't work, both because of the actual topic of this question and because I haven't yet figured out how to elegantly make awk join $2..$n into a single variable. (But that's the topic of a possible future question.)
FWIW, I'm using FreeBSD 9.2 with its built in, but I'm open to using gawk if a solution can be found with that.
Why so lengthy and complicated an example? This demonstrates the problem:
$ echo "" | awk '{s="a\t%s"; printf s"\n","b"}'
a b
$ echo "a\t%s" | awk '{s=$0; printf s"\n","b"}'
a\tb
In the first case, the string "a\t%s" is a string literal and so is interpreted twice - once when the script is read by awk and then again when it is executed, so the \t is expanded on the first pass and then at execution awk has a literal tab char in the formatting string.
In the second case awk still has the characters backslash and t in the formatting string - hence the different behavior.
You need something to interpret those escaped chars and one way to do that is to call the shell's printf and read the results (corrected per #EtanReiser's excellent observation that I was using double quotes where I should have had single quotes, implemented here by \047, to avoid shell expansion):
$ echo 'a\t%s' | awk '{"printf \047" $0 "\047 " "b" | getline s; print s}'
a b
If you don't need the result in a variable, you can just call system().
If you just wanted the escape chars expanded so you don't need to provide the %s args in the shell printf call, you'd just need to escape all the %s (watching out for already-escaped %s).
You could call awk instead of the shell printf if you prefer.
Note that this approach, while clumsy, is much safer than calling an eval which might just execute an input line like rm -rf /*.*!
With help from Arnold Robbins (the creator of gawk), and Manuel Collado (another noted awk expert), here is a script which will expand single-character escape sequences:
$ cat tst2.awk
function expandEscapes(old, segs, segNr, escs, idx, new) {
split(old,segs,/\\./,escs)
for (segNr=1; segNr in segs; segNr++) {
if ( idx = index( "abfnrtv", substr(escs[segNr],2,1) ) )
escs[segNr] = substr("\a\b\f\n\r\t\v", idx, 1)
new = new segs[segNr] escs[segNr]
}
return new
}
{
s = expandEscapes($0)
printf s, "foo", "bar"
}
.
$ awk -f tst2.awk <<<"hello: %s\nworld: %s\n"
hello: foo
world: bar
Alternatively, this shoudl be functionally equivalent but not gawk-specific:
function expandEscapes(tail, head, esc, idx) {
head = ""
while ( match(tail, /\\./) ) {
esc = substr( tail, RSTART + 1, 1 )
head = head substr( tail, 1, RSTART-1 )
tail = substr( tail, RSTART + 2 )
idx = index( "abfnrtv", esc )
if ( idx )
esc = substr( "\a\b\f\n\r\t\v", idx, 1 )
head = head esc
}
return (head tail)
}
If you care to, you can expand the concept to octal and hex escape sequences by changing the split() RE to
/\\(x[0-9a-fA-F]*|[0-7]{1,3}|.)/
and for a hex value after the \\:
c = sprintf("%c", strtonum("0x" rest_of_str))
and for an octal value:
c = sprintf("%c", strtonum("0" rest_of_str))
Since the question explicitly asks for an awk solution, here's one which works on all the awks I know of. It's a proof-of-concept; error handling is abysmal. I've tried to indicate places where that could be improved.
The key, as has been noted by various commentators, is that awk's printf -- like the C standard function it is based on -- does not interpret backslash-escapes in the format string. However, awk does interpret them in command-line assignment arguments.
awk 'BEGIN {if(ARGC!=3)exit(1);
fn=ARGV[2];ARGC=2}
NR==FNR{ARGV[ARGC++]="fmt="substr($0,length($1)+2);
ARGV[ARGC++]="fmtid="$1;
ARGV[ARGC++]=fn;
next}
{match($0,/^ *[^ ]+[ ]+[^ ]+[ ]+/);
printf fmt,$1,$2,substr($0,RLENGTH+1) > ("data/"fmtid"/"$1)
}' fmtfile sampledata
(
What's going on here is that the 'FNR==NR' clause (which executes only on the first file) adds the values (fmtid, fmt) from each line of the first file as command-line assignments, and then inserts the data file name as a command-line argument. In awk, assignments as command line arguments are simply executed as though they were assignments from a string constant with implicit quotes, including backslash-escape processing (except that if the last character in the argument is a backslash, it doesn't escape the implicit closing double-quote). This behaviour is mandated by Posix, as is the order in which arguments are processed which makes it possible to add arguments as you go.
As written, the script must be provided with exactly two arguments: the formats and the data (in that order). There is some room for improvement, obviously.
The snippet also shows two ways of concatenating trailing fields.
In the format file, I assume that the lines are well behaved (no leading spaces; exactly one space after the format id). With those constraints, substr($0, length($1)+2) is precisely the part of the line after the first field and a single space.
Processing the datafile, it may be necessary to do this with fewer constraints. First, the builtin match function is called with the regular expression /^ *[^ ]+[ ]+[^ ]+[ ]+/ which matches leading spaces (if any) and two space-separated fields, along with the following spaces. (It would be better to allow tabs, as well.) Once the regex matches (and matching shouldn't be assumed, so there's another thing to fix), the variables RSTART and RLENGTH are set, so substr($0, RLENGTH+1) picks up everything starting with the third field. (Again, this is all Posix-standard behaviour.)
Honestly, I'd use the shell printf for this problem, and I don't understand why you feel that solution is somehow sub-optimal. The shell printf interprets backslash escapes in formats, and the shell read -r will do the line splitting the way you want. So there's no reason for awk at all, as far as I can see.
Ed Morton shows the problem clearly (edit: and it's now complete, so just go accept it): awk's string literal processing handled the escapes, and file I/O code isn't a lexical analyzer.
It's an easy fix: decide what escapes you want to support, and support them. Here's a one-liner form if you're doing special-purpose work that doesn't need to handle escaped backslashes
awk '{ gsub(/\\n/,"\n"); gsub(/\\t/,"\t"); printf($0 "bar\n", "world"); }' <<\EOD
hello:\t%s\n\tfoo
EOD
but for doit-and-forgetit peace of mind just use the full form in the linked answer.
#Ed Morton's answer explains the problem well.
A simple workaround is to:
pass the format-string file contents via an awk variable, using command substitution,
assuming that file is not too large to be read into memory in full.
Using GNU awk or mawk:
awk -v formats="$(tr '\n' '\3' <fmtStrings)" '
# Initialize: Split the formats into array elements.
BEGIN {n=split(formats, aFormats, "\3")}
# For each data line, loop over all formats and print.
{ for(i=1;i<n;++i) {printf aFormats[i] "\n", $1, $2, $3} }
' sampleData
Note:
The advantage of this solution is that it works generically - you don't need to anticipate specific escape sequences and handle them specially.
On FreeBSD awk, this almost works, but - sadly - split() still splits by newlines, despite being given an explicit separator - this smells like a bug. Observed on versions 20070501 (OS X 10.9.4) and 20121220 (FreeBSD 10.0).
The above solves the core problem (for brevity, it omits stripping the ID from the front of the format strings and omits the output-file creation logic).
Explanation:
tr '\n' '\3' <fmtStrings replaces actual newlines in the format-strings file with \3 (0x3) characters, so as to be able to later distinguish them from the \n escape sequences embedded in the lines, which awk turns into actual newlines when assigning to variable formats (as desired).
\3 (0x3) - the ASCII end-of-text char. - was arbitrarily chosen as an auxiliary separator that is assumed not to be present in the input file.
Note that using \0 (NUL) is NOT an option, because awk interprets that as an empty string, causing split() to split the string into individual characters.
Inside the BEGIN block of the awk script, split(formats, aFormats, "\3") then splits the combined format strings back into individual format strings.
I had to create another answer to start clean, I believe I've come to a good solution, again with perl:
echo '%10s\t:\t%10s\r\n' | perl -lne 's/((?:\\[a-zA-Z\\])+)/qq[qq[$1]]/eeg; printf "$_","hi","hello"'
hi : hello
That bad boy s/((?:\\[a-zA-Z\\])+)/qq[qq[$1]]/eeg will translate any meta character I can think of, let us take a look with cat -A :
echo '%10s\t:\t%10s\r\n' | perl -lne 's/((?:\\[a-zA-Z\\])+)/qq[qq[$1]]/eeg; printf "$_","hi","hello"' | cat -A
hi^I:^I hello^M$
PS. I didn't create that regex, I googled unquote meta and found here
What you are trying to do is called templating. I would suggest that shell tools are not the best tools for this job. A safe way to go would be to use a templating library such as Template Toolkit for Perl, or Jinja2 for Python.
The problem lies in the non-interpretation of the special characters \t and \n by echo: it makes sure that they are understood as as-is strings, and not as tabulations and newlines. This behavior can be controlled by the -e flag you give to echo, without changing your awk script at all:
echo -e "hello:\t%s\n\tfoo" | awk '{s=$0; printf(s "bar\n", "world");}'
tada!! :)
EDIT:
Ok, so after the point rightfully raised by Chrono, we can devise this other answer corresponding to the original request to have the pattern read from a file:
echo "hello:\t%s\n\tfoo" > myfile
awk 'BEGIN {s="'$(cat myfile)'" ; printf(s "bar\n", "world")}'
Of course in the above we have to be careful with the quoting, as the $(cat myfile) is not seen by awk but interpreted by the shell.
This looks extremely ugly, but it works for this particular problem:
s=$0;
gsub(/'/, "'\\''", s);
gsub(/\\n/, "\\\\\\\\n", s);
"printf '%b' '" s "'" | getline s;
gsub(/\\\\n/, "\n", s);
gsub(/\\n/, "\n", s);
printf(s " bar\n", "world");
Replace all single quotes with shell-escaped single quotes ('\'').
Replace all escaped newline sequences that appear normally as \n with the sequence that appears as \\\\n. It would suffice to use \\\\n as the actual replacement string (meaning \\n would print if you printed it), but the version of gawk I have messes things up in POSIX mode.
Invoke the shell to execute printf '%b' 'escape'\''d format' and use awk's getline statement to retrieve the line.
Unescape \\n to yield a newline. This step wouldn't be necessary if gawk in POSIX mode played nicely.
Unescape \n to yield a newline.
Otherwise you're left to call the gsub function for each possible escape sequence, which is terrible for \001, \002, etc.
Graham,
Ed Morton's solution is the best (and perhaps only) one available.
I'm including this answer for a better explanation of WHY you're seeing what you're seeing.
A string is a string. The confusing part here is WHERE awk does the translation of \t to a tab, \n to a newline, etc. It appears NOT to be the case that the backslash and t get translated when used in a printf format. Instead, the translation happens at assignment, so that awk stores the tab as part of the format rather than translating when it runs the printf.
And this is why Ed's function works. When read from stdin or a file, no assignment is performed that will implement the translation of special characters. Once you run the command s="a\tb"; in awk, you have a three character string containing no backslash or t.
Evidence:
$ echo "a\tb\n" | awk '{ s=$0; for (i=1;i<=length(s);i++) {printf("%d\t%c\n",i,substr(s,i,1));} }'
1 a
2 \
3 t
4 b
5 \
6 n
vs
$ awk 'BEGIN{s="a\tb\n"; for (i=1;i<=length(s);i++) {printf("%d\t%c\n",i,substr(s,i,1));} }'
1 a
2
3 b
4
And there you go.
As I say, Ed's answer provides an excellent function for what you need. But if you can predict what your input will look like, you can probably get away with a simpler solution. Knowing how this stuff gets parsed, if you have a limited set of characters you need to translate, you may be able to survive with something simple like:
s=$0;
gsub(/\\t/,"\t",s);
gsub(/\\n/,"\n",s);
That's a cool question, I don't know the answer in awk, but in perl you can use eval :
echo '%10s\t:\t%-10s\n' | perl -ne ' chomp; eval "printf (\"$_\", \"hi\", \"hello\")"'
hi : hello
PS. Be aware of code injection danger when you use eval in any language, no just eval any system call can't be done blindly.
Example in Awk:
echo '$(whoami)' | awk '{"printf \"" $0 "\" " "b" | getline s; print s}'
tiago
What if the input was $(rm -rf /)? You can guess what would happen :)
ikegami adds:
Why would even think of using eval to convert \n to newlines and \t to tabs?
echo '%10s\t:\t%-10s\n' | perl -e'
my %repl = (
n => "\n",
t => "\t",
);
while (<>) {
chomp;
s{\\(?:(\w)|(\W))}{
if (defined($2)) {
$2
}
elsif (exists($repl{$1})) {
$repl{$1}
}
else {
warn("Unrecognized escape \\$1.\n");
$1
}
}eg;
printf($_, "hi", "hello");
}
'
Short version:
echo '%10s\t:\t%-10s\n' | perl -nle'
s/\\(?:(n)|(t)|(.))/$1?"\n":$2?"\t":$3/seg;
printf($_, "hi", "hello");
'