hash using sha1sum using awk - hash

Question

I have a "pipe-separated" file that has about 20 columns. I want to just hash the first column which is a number like account number using sha1sum and return the rest of the columns as is.
Whats the best way I can do this using awk or sed?
Accountid|Time|Category|.....
8238438|20140101021301|sub1|...
3432323|20140101041903|sub2|...
9342342|20140101050303|sub1|...
Above is an example of the text file showing just 3 columns. Only the first column has the hashfunction implemented on it. Result should like:
Accountid|Time|Category|.....
104a1f34b26ae47a67273fe06456be1fe97f75ba|20140101021301|sub1|...
c84270c403adcd8aba9484807a9f1c2164d7f57b|20140101041903|sub2|...
4fa518d8b005e4f9a085d48a4b5f2c558c8402eb|20140101050303|sub1|...

Answer 1

What the Best Way™ is is up for debate. One way to do it with awk is
awk -F'|' 'BEGIN { OFS=FS } NR == 1 { print } NR != 1 { gsub(/'\''/, "'\'\\\\\'\''", $1); command = ("echo '\''" $1 "'\'' | sha1sum -b | cut -d\\ -f 1"); command | getline hash; close(command); $1 = hash; print }' filename
That is
BEGIN {
OFS = FS # set output field separator to field separator; we will use
# it because we meddle with the fields.
}
NR == 1 { # first line: just print headers.
print
}
NR != 1 { # from there on do the hash/replace
# this constructs a shell command (and runs it) that echoes the field
# (singly-quoted to prevent surprises) through sha1sum -b, cuts out the hash
# and gets it back into awk with getline (into the variable hash)
# the gsub bit is to prevent the shell from barfing if there's an apostrophe
# in one of the fields.
gsub(/'/, "'\\''", $1);
command = ("echo '" $1 "' | sha1sum -b | cut -d\\ -f 1")
command | getline hash
close(command)
# then replace the field and print the result.
$1 = hash
print
}
You will notice the differences between the shell command at the top and the awk code at the bottom; that is all due to shell expansion. Because I put the awk code in single quotes in the shell commands (double quotes are not up for debate in that context, what with $1 and all), and because the code contains single quotes, making it work inline leads to a nightmare of backslashes. Because of this, my advice is to put the awk code into a file, say foo.awk, and run
awk -F'|' -f foo.awk filename
instead.

Answer 2

Here's an awk executable script that does what you want:
#!/usr/bin/awk -f
BEGIN { FS=OFS="|" }
FNR != 1 { $1 = encodeData( $1 ) }
47
function encodeData( fld ) {
cmd = sprintf( "echo %s | sha1sum", fld )
cmd | getline output
close( cmd )
split( output, arr, " " )
return arr[1]
}
Here's the flow break down:
Set the input and output field separators to |
When the row isn't the first (header) row, re-assign $1 to an encoded value
Print the entire row when 47 is true (always)
Here's the encodeData function break down:
Create a cmd to feed data to sha1sum
Feed it to getline
Close the cmd
On my system, there's extra info after sha1sum, so I discard it by spliting the output
Return the first field of the sha1sum output.
With your data, I get the following:
Accountid|Time|Category|.....
104a1f34b26ae47a67273fe06456be1fe97f75ba|20140101021301|sub1|...
c84270c403adcd8aba9484807a9f1c2164d7f57b|20140101041903|sub2|...
4fa518d8b005e4f9a085d48a4b5f2c558c8402eb|20140101050303|sub1|...
running by calling awk.script data (or ./awk.script data if you bash)
EDIT by EdMorton:
sorry for the edit, but your script above is the right approach but needs some tweaks to make it more robust and this is much easier than trying to describe them in a comment:
$ cat tst.awk
BEGIN { FS=OFS="|" }
NR==1 { for (i=1; i<=NF; i++) f[$i] = i; next }
{ $(f["Accountid"]) = encodeData($(f["Accountid"])); print }
function encodeData( fld, cmd, output ) {
cmd = "echo \047" fld "\047 | sha1sum"
if ( (cmd | getline output) > 0 ) {
sub(/ .*/,"",output)
}
else {
print "failed to hash " fld | "cat>&2"
output = fld
}
close( cmd )
return output
}
$ awk -f tst.awk file
104a1f34b26ae47a67273fe06456be1fe97f75ba|20140101021301|sub1|...
c84270c403adcd8aba9484807a9f1c2164d7f57b|20140101041903|sub2|...
4fa518d8b005e4f9a085d48a4b5f2c558c8402eb|20140101050303|sub1|...
The f[] array decouples your script from hard-coding the number of the field that needs to be hashed, the additional args for your function make them local and so always null/zero on each invocation, the if on getline means you won't return the previous success value if it fails (see http://awk.info/?tip/getline) and the rest is maybe more style/preference with a bit of a performance improvement.