I am new to shell scripting and I am encountering some issue with my codes. Currently, I have this line of code which is able to run perfectly on my terminal which will give me the result which I am looking for:
cat BookDB.txt | awk -F ":" '$1 ~ $Title'
However, when I try to implement this into my script, no result is shown. Anyone able to help me with this problem?
Is $Title supposed to be a shell variable? If so, the shell can't substitute it because the awk body is in single quotes. Use awk's -v option to pass shell variables into awk:
awk -F : -v "title=$Title" '$1 ~ title' BookDB.txt
See also https://en.wikipedia.org/wiki/Cat_(Unix)#Useless_use_of_cat
Related
Is it possible to store an awk script inside a shell variable; for example:
export script="'{printf(\$2); printf("\"\\n\"");}'"
echo $script
'{printf($2); printf("\n");}'
The script functions properly when I call it directly as such:
awk '{printf($2); printf("\n");}' testFile.txt
prints proper output
When I try and pass the script as a shell variable, I run into issues.
awk $script testFile.txt
awk: syntax error at source line 1
context is
>>> ' <<<
missing }
awk: bailing out at source line 1
I get a slightly different error when I wrap the variable in double quotes
awk "$script" testFile.txt
awk: syntax error at source line 1
context is
>>> ' <<<
awk: bailing out at source line 1
I'm still learning exactly how shell expansions work, I would appreciate any suggestions about what I am missing here.
Error in your quoting
export script='{printf($2); printf("\n");}'
awk "${script}" YourFile
I am not sure about the proper answer to this, but a very ugly (and probably unstable depending on the $script contents) workaround would be:
echo $script | awk '{print "awk "$0" testFile.txt"}' | bash
This is just printing the contents of $script in an awk statement that is then executed by bash. I am not particularly proud of this, but maybe it helps!
When you type
awk '{printf($2); printf("\n");}' testFile.txt
awk only sees {printf($2); printf("\n");} -- the shell removes the quotes
(see Quote Removal in the bash manual)
Heed #NeronLeVelu's answer.
I'm on a Mac, and I want to find a field in a CSV file adjacent to a search string
This is going to be a single file with a hard path; here's a sample of it:
84:a5:7e:6c:a6:b0, AP-ATC-151g84
84:a5:7e:6c:a6:b1, AP-A88-131g84
84:a5:7e:73:10:32, AP-AG7-133g56
84:a5:7e:73:10:30, AP-ADC-152g81
84:a5:7e:73:10:31, AP-D78-152e80
so if my search string is "84:a5:7e:73:10:32"
I want to get returned "AP-AG7-133g56"
I had been working within an Applescript, but maybe a shell script will do.
I just need the proper syntax for opening the file and having awk search it. Again, I'm weak conceptually on how shell commands run, how they must be executed, etc
This errors, gives me ("command not found"):
set the_file to "/Users/Paw/Desktop/AP-Decoder 3.app/Contents/Resources/BSSIDtable.csv"
set the_val to "70:56:81:cb:a2:dc"
do shell script "'awk $1 ~ the_val {print $2} the_file'"
Thank you for coddling me...
This is a relatively simple:
awk '$1 == "70:56:81:cb:a2:dc," {print "The answer is "$2}' 'BSSIDtable.csv'
(the "The answer is " text can be omitted if you only wish to see only the data, but this shows you how to get more user-friendly output if desired).
The comma is included since awk uses white space for separators so the comma becomes part of column 1.
If the thing you're looking for is in a shell variable, you can use -v to provide that to awk as an awk variable:
lookfor="70:56:81:cb:a2:dc,"
awk -v mac=$lookfor '$1 == mac {print "The answer is "$2}' 'BSSIDtable.csv'
As an aside, your AppleScript solution is probably not working because the $1/$2 are being interpreted as shell variable rather than awk variables. If you insist on using AppleScript, you will have to figure out how to construct a shell command that quotes the awk commands correctly.
My advice is to just use the shell directly, the number of people proficient in that almost certainly far outnumber those proficient in AppleScript :-)
if sed is available (normaly on mac, event if not tagged in OP)
simple but read all the file
sed -n 's/84:a5:7e:73:10:32,[[:blank:]]*//p' YourFile
quit after first occurence (so average of 50% faster on huge file)
sed -n -e '/84:a5:7e:73:10:32,[[:blank:]]*/!b' -e 's///p;q' YourFile
awk
awk '/^84:a5:7e:73:10:32/ {print $2}'
# OR using a variable for batch interaction
awk -v Src='84:a5:7e:73:10:32' '$1 == Src {print $2}'
# OR assuming that case is unknow
awk -v Src='84:a5:7e:73:10:32' 'BEGIN{IGNORECASE=1} $1 == Src {print $2}'
by default it take $0 as compare test if a regex is present, just add the ^ to take first field content
I am having a little trouble with using a variable and printing the 2nd field with the awk command. I am attempting to grab a number from a value in a file. The value in the file looks like
MAX=10000 (I want the Number only), I am passing this into a variable in a script so in the script I have variables
parm_file=ParmFiles/Parmfile.parm
session=s_session_value
OLD_MAX_SEQ_NR=`awk -F '=' "/$session/ {getline; print $2}" < $parm_file`
because I have double quotes to identify the $session variable, it is taking the $2 as a variable too, and so it is just printing the whole line, instead of the second field.
I've tried also to pass the variable into the awk command like
OLD_MAX_SEQ_NR=`awk -F '=' \
-v var="$session" \
'/var/ {getline; print $2}' < $parm_file`
But it does not seem to be putting the variable where var is. I have even tried hard coding the -v var="s_session_value" and it does not work.
I can't figure out a way to make the command look at the $2 as it normally does instead of a variable. Any help would be greatly appreciated.
Try this:
parm_file=ParmFiles/Parmfile.parm
session=s_session_value
OLD_MAX_SEQ_NR=$(
awk -F'=' -v pat="$session" \
'$0 ~ pat {getline; print $2}' < "$parm_file"
)
You need to pass shell variables to awk by defining an awk variable using -v.
Using variable inside /../ is taken as literal. So use $0~var_name construct.
Using back-ticks is deprecated. Use command substitution $(..)
Quote your variables.
It's a bit tricky without a sample line of the parm file. But I don't understand why you don't use cut, it makes it much easier?
OLD_MAX_SEQ_NR=$(grep "$session" "$parm_file" | cut -d= -f2)
I am trying to execute a shell script in which I am trying to open the file /sys/class/power_supply/BAT0/status through awk. But, the script fails to execute saying that the file cannot be read. Even executing the script with sudo does not work. Below is the script. I am on Kubuntu 13.10. I searched a lot, but couldn't find a solution. Thanks for the help!
#!/bin/sh
awk '{
echo $0
}' | /sys/class/power_supply/BAT0/status
The general form of an awk command is:
awk '<awk script commands>' input-file
As status is the input file it should follow the awk scripting. The pipe symbol does not make sense here.
#!/bin/sh
awk '{
print $0
}' /sys/class/power_supply/BAT0/status
I am new to awk.I just try to write some thing that to exchange my text file.but I failed.
I want to output like 'hello'.
I used command awk '{print "'hello'"}' filename to do it.but failed:
output like: hello
but I used command awk '{print "\'hello\'"}' filename to do it.failed again:
output like: >
ok.it seems that the awk command do not get what I mean.
So I am confused about that .how to solve the problem.
guys thanks.
Using the ascii code:
awk '{print "\x27" "hello" "\x27"}' filename
Using a variable:
awk -v q="'" '{print q "hello" q}' filename
Example:
$ seq 2 > filename
$ awk '{print "\x27" "hello" "\x27"}' filename
'hello'
'hello'
$ awk -v q="'" '{print q "hello" q}' filename
'hello'
'hello'
Simply use double quotes:
awk "{print \"'hello'\"}" filename
Although that won't really modify your file.
awk '{print "'"'"'hello'"'"'"}' filename
clyfish's answer works, if you must have it output single quotes and you must use scripts that you pass on the command line.
What I usually do in cases like these, though, when I need to do quoting but I don't want to write a 'real' awk script, is this:
awk 'function q(word) { return "\"" word "\"" }
{ printf("mv %s SomeDir/;", q($0)) }'
What I've done is to define a function that returns whatever you pass it in double quotes. Then use printf to actually use it. Without doing that, I would have had to do:
awk '{ print("mv \"" $0 "\" SomeDir/;") }';
It gets pretty nasty. For more complicated examples, this can be a life saver.
However, suppose you really do need to output something with actual single quotes. In that case dealing with odd shell quoting rules while trying to pass scripts like this on the command line is going to drive you completely insane, so I would suggest you just write a simple throwaway file.
#!/usr/bin/awk
# hi.awk
{ print("'hello'") }
then call it:
awk -f ./hi.awk
You don't really even need the #! line in the file if you do it that way, but neither does it hurt.