How do I use shell variables of awk script in system command?

Question

I am troubleing in coverting hex to decimal from txt file using awk.

I want to do like this

awk -F' '   '{   system("echo '$((16#"$1"))'") '} $file_name

but not work... then I try other code

awk -F' ' -v var="\"echo \x27\$((16#" '{var=var$1"))\x27\"" system(var) }' $file_name

also not work. but print var then enter image description here

what should i do?

Please include content as text, not behind image links. See Why not upload images of code on SO when asking a question? -- the reasoning regarding searchability, accessibility, access to folks behind corporate firewalls, bandwidth expenditures, &c. apply for errors as well. — Charles Duffy
– Charles Duffy, Commented Jan 11, 2018 at 4:44
Also, frankly, using the system() command in awk is a code smell -- you're much better off not using awk at all if you'd be pushing all the work from awk back to a shell. system() is not just inefficient, but its use runs major security risks. — Charles Duffy
– Charles Duffy, Commented Jan 11, 2018 at 4:45
@Charless Duffy sorry to upload image links, next time I must upload code, then not using awk, not using system() , As result, What can I use it? — bestn
– bestn, Commented Jan 11, 2018 at 5:21
either awk only, or bash only; John's answer covers both. system() is dangerous because everything it passes is parsed as code, so malicious data can run arbitrary commands; you don't have that problem when handling data in bash unless eval or equivalents are used, nor do you have it in native awk. — Charles Duffy
– Charles Duffy, Commented Jan 11, 2018 at 5:25
@Charless Duffy ok, I understand, then I want script code in either awk only or bash only, I don't know using only one way either awk only or bash only — bestn
– bestn, Commented Jan 11, 2018 at 5:34

John1024 · Accepted Answer · 2018-01-11 06:57:09Z

3

Using awk

To use GNU awk to convert hex to decimal:

$ echo '0xFFFFFFFE' | awk -n '{printf "%i\n",$1}'
4294967294

Or:

$ x='0xFFFFFFFE'
$ awk -n -v x="$x"  'BEGIN{printf "%i\n",x}'
4294967294

Or:

$ x='0xFFFFFFFE'; awk -v x="$x"  'BEGIN{print strtonum(x)}'
4294967294

To convert hex to decimal using bash:

$ echo $((0xFFFFFFFE))
4294967294

Limitations:

1. GNU awk is limited to 52-bit integers.

2. The above could be extended to perform two's-complement arithmetic but it hasn't.

To avoid both these limitations, see the python solution below:

Using python

Awk does not handle long integers. For long integers, consider this python script:

$ cat n.py
#!/usr/bin/python3
import sys
def h(x):
        x = int(x, 16)
        return x if x < 2**63 else x - 2**64

for line in sys.stdin:
        print(*[h(x) for x in line.split()])

Let's use this input file:

$ cat file
FFFFFFFFFFFFFFFF EFEFEFEFEFEFEFEF

When we run our script, we find:

$ python3 n.py <file
-1 -1157442765409226769

edited Jan 11, 2018 at 6:57

answered Jan 11, 2018 at 4:47

John1024

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16 Comments

bestn Over a year ago

my file's contens are FFFFFFFFFFFFFFFF EFEFEFEFEFEFEFEF and I want to read and convert hex to long type(int64)!

John1024 Over a year ago

@bestn Are those two numbers on one line or on two lines?

bestn Over a year ago

2 colums per 1 row and I think I must use echo like "echo $((16#FF))", don't it?

David C. Rankin Over a year ago

Then do the same thing using "$2" to handle the second field.

bestn Over a year ago

@John1024 AMAZING~! Thank you! god python!

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