Hi I am having a shell script ,
the shell script has a variable named RESPONSE
I want a to check if the json object has an attribute named "address" is present. Also how to get value of the attribute address . I want to use jq library
#!/bin/bash
RESPONSE={"content-length":"2","address":"192.168.123.1","path":"/hello-world"}
appreciate any help
jq '.address' will output the value of the property value, e.g. "192.168.123.1". (jq -r to get rid of the quote marks)
jq 'has(.address)' will output true/false
jq -e 'has(.address)' >/dev/null will set the process' exit status to 0/1 depending on the object having the key "address" (regardless of value)
jq -e '.address' >/dev/null will set the process' exit status to 0 if the "address" property has a truthy value (anything except null or false). A null or false valued property will set the exit code to 1.
Having the appropriate exit status allows you to do things such as:
if jq -e '.address' >/dev/null; then
echo 'object has address field'
fi
# or:
jq -e 'has(.address)' >/dev/null || echo 'object does not have an address'
I am trying to parse my curl output with JQ and check the exit code, so when my curl output is empty, JQ return 0 exit code.
For example:
$ echo "" | jq '.key'
$ echo $?
0
How to make this return 1 or some non-zero value?
You should use input with -n/--null-input on the command line. This way JQ will fail if its input is empty.
$ echo | jq -n 'input.key'
jq: error (at <stdin>:1): break
$ echo $?
5
$ jq -n '{key: 1}' | jq -n 'input.key'
1
$ echo $?
0
If you want to specify the return code when the input is empty, you could use halt_error/1, like so:
$ echo "" | jq -n 'try input.key catch halt_error(9)' 2> /dev/null
$ echo $?
9
Let's pretend I'm running something like this:
jq -nr --arg target /tmp \
'(["echo","Hello, world"]|#sh)+">\($target)/sample.txt"' \
| sh
Everything is fine unless I forgot to pass variable $target:
$ jq -nr '(["echo","Hello, world"]|#sh)+">\($target)/sample.txt"'
jq: error: $target is not defined at <top-level>, line 1:
(["echo","Hello, world"]|#sh)+">\($target)/sample.txt"
jq: 1 compile error
How can I catch this and use default value?
I've tried:
$target?
($target)?
try $target catch null
$target? // null
But it seems to be parsing-time error, which obviously can't be caught at runtime. Have I've missed any dynamic syntax?
I've found that command-line arguments can be found in $ARGS.name, but there are two drawbacks:
This was introduced in version 1.6, but I have 1.5 on CentOS 7.
It doesn't catch locally defined variables.
Assuming you need to do something more useful with jq than write 'Hello World' over a text file. I propose the following,
Maybe we can learn some programming tips from Jesus:
"Give to Caesar what belongs to Caesar, and give to God what belongs to God"
Suppose that Caesar is bash shell and God is jq, bash is appropriate to work and test the existence of files, directories and environment variables, jq is appropriate to process information in json format.
#!/bin/bash
dest_folder=$1
#if param1 is not given, then the default is /tmp:
if [ -z $dest_folder ]; then dest_folder=/tmp ; fi
echo destination folder: $dest_folder
#check if destination folder exists
if [ ! -d $dest_folder ]
then
echo "_err_ folder not found"
exit 1
fi
jq -nr --arg target $dest_folder '(["echo","Hello, world"]|#sh)+">\($target)/sample.txt"' | sh
#if the file is succesfully created, return 0, if not return 1
if [ -e "$dest_folder/sample.txt" ]
then
echo "_suc_ file was created ok"
exit 0
else
echo "_err_ when creating file"
exit 1
fi
Now you can include this script as a step in a more complex batch, because it is congruent with linux style, returning 0 on success.
I am using jq to search for specific results in a large file. I do not care for duplicate entries matching this specific condition, and it takes a while to process the whole file. What I would like to do is print some details about the first match and then terminate the jq command on the file to save time.
I.e.
jq '. | if ... then "print something; exit jq" else ... end'
I looked into http://stedolan.github.io/jq/manual/?#Breakingoutofcontrolstructures but this didn't quite seem to apply
EDIT:
The file I am parsing contains multiple json objects, one after another. They are not in an array.
Here is an approach which uses a recent version of first/1 (currently in master)
def first(g): label $out | g | ., break $out;
first(inputs | if .=="100" then . else empty end)
Example:
$ seq 1000000000 | jq -M -Rn -f filter.jq
Output (followed by immediate termination)
"100"
Here I use seq in lieu of a large JSON dataset.
To do what is requested is possible using features that were added after the release of jq 1.4. The following uses foreach and inputs:
label $top
| foreach inputs as $line
# state: true means found; false means not yet found
(false;
if . then break $top
else if $line | tostring | test("goodbye") then true else false end
end;
if . then $line else empty end
)
Example:
$ cat << EOF | jq -n -f exit.jq
1
"goodbye"
3
4
EOF
Result:
"goodbye"
You can accomplish it using halt and the inputs builtin:
jq -n 'inputs | if ... then "something", halt else ... end'
Will print "something" and terminate gracefully when the condition matches.
For this to work (i.e. terminate when condition is true), jq needs the -n parameter. See this issue
I have a fixed-width-field file which I'm trying to sort using the UNIX (Cygwin, in my case) sort utility.
The problem is there is a two-line header at the top of the file which is being sorted to the bottom of the file (as each header line begins with a colon).
Is there a way to tell sort either "pass the first two lines across unsorted" or to specify an ordering which sorts the colon lines to the top - the remaining lines are always start with a 6-digit numeric (which is actually the key I'm sorting on) if that helps.
Example:
:0:12345
:1:6:2:3:8:4:2
010005TSTDOG_FOOD01
500123TSTMY_RADAR00
222334NOTALINEOUT01
477821USASHUTTLES21
325611LVEANOTHERS00
should sort to:
:0:12345
:1:6:2:3:8:4:2
010005TSTDOG_FOOD01
222334NOTALINEOUT01
325611LVEANOTHERS00
477821USASHUTTLES21
500123TSTMY_RADAR00
(head -n 2 <file> && tail -n +3 <file> | sort) > newfile
The parentheses create a subshell, wrapping up the stdout so you can pipe it or redirect it as if it had come from a single command.
If you don't mind using awk, you can take advantage of awk's built-in pipe abilities
eg.
extract_data | awk 'NR<3{print $0;next}{print $0| "sort -r"}'
This prints the first two lines verbatim and pipes the rest through sort.
Note that this has the very specific advantage of being able to selectively sort parts
of a piped input. all the other methods suggested will only sort plain files which can be read multiple times. This works on anything.
In simple cases, sed can do the job elegantly:
your_script | (sed -u 1q; sort)
or equivalently,
cat your_data | (sed -u 1q; sort)
The key is in the 1q -- print first line (header) and quit (leaving the rest of the input to sort).
For the example given, 2q will do the trick.
The -u switch (unbuffered) is required for those seds (notably, GNU's) that would otherwise read the input in chunks, thereby consuming data that you want to go through sort instead.
Here is a version that works on piped data:
(read -r; printf "%s\n" "$REPLY"; sort)
If your header has multiple lines:
(for i in $(seq $HEADER_ROWS); do read -r; printf "%s\n" "$REPLY"; done; sort)
This solution is from here
You can use tail -n +3 <file> | sort ... (tail will output the file contents from the 3rd line).
head -2 <your_file> && nawk 'NR>2' <your_file> | sort
example:
> cat temp
10
8
1
2
3
4
5
> head -2 temp && nawk 'NR>2' temp | sort -r
10
8
5
4
3
2
1
It only takes 2 lines of code...
head -1 test.txt > a.tmp;
tail -n+2 test.txt | sort -n >> a.tmp;
For a numeric data, -n is required. For alpha sort, the -n is not required.
Example file:
$ cat test.txt
header
8
5
100
1
-1
Result:
$ cat a.tmp
header
-1
1
5
8
100
So here's a bash function where arguments are exactly like sort. Supporting files and pipes.
function skip_header_sort() {
if [[ $# -gt 0 ]] && [[ -f ${#: -1} ]]; then
local file=${#: -1}
set -- "${#:1:$(($#-1))}"
fi
awk -vsargs="$*" 'NR<2{print; next}{print | "sort "sargs}' $file
}
How it works. This line checks if there is at least one argument and if the last argument is a file.
if [[ $# -gt 0 ]] && [[ -f ${#: -1} ]]; then
This saves the file to separate argument. Since we're about to erase the last argument.
local file=${#: -1}
Here we remove the last argument. Since we don't want to pass it as a sort argument.
set -- "${#:1:$(($#-1))}"
Finally, we do the awk part, passing the arguments (minus the last argument if it was the file) to sort in awk. This was orignally suggested by Dave, and modified to take sort arguments. We rely on the fact that $file will be empty if we're piping, thus ignored.
awk -vsargs="$*" 'NR<2{print; next}{print | "sort "sargs}' $file
Example usage with a comma separated file.
$ cat /tmp/test
A,B,C
0,1,2
1,2,0
2,0,1
# SORT NUMERICALLY SECOND COLUMN
$ skip_header_sort -t, -nk2 /tmp/test
A,B,C
2,0,1
0,1,2
1,2,0
# SORT REVERSE NUMERICALLY THIRD COLUMN
$ cat /tmp/test | skip_header_sort -t, -nrk3
A,B,C
0,1,2
2,0,1
1,2,0
Here's a bash shell function derived from the other answers. It handles both files and pipes. First argument is the file name or '-' for stdin. Remaining arguments are passed to sort. A couple examples:
$ hsort myfile.txt
$ head -n 100 myfile.txt | hsort -
$ hsort myfile.txt -k 2,2 | head -n 20 | hsort - -r
The shell function:
hsort ()
{
if [ "$1" == "-h" ]; then
echo "Sort a file or standard input, treating the first line as a header.";
echo "The first argument is the file or '-' for standard input. Additional";
echo "arguments to sort follow the first argument, including other files.";
echo "File syntax : $ hsort file [sort-options] [file...]";
echo "STDIN syntax: $ hsort - [sort-options] [file...]";
return 0;
elif [ -f "$1" ]; then
local file=$1;
shift;
(head -n 1 $file && tail -n +2 $file | sort $*);
elif [ "$1" == "-" ]; then
shift;
(read -r; printf "%s\n" "$REPLY"; sort $*);
else
>&2 echo "Error. File not found: $1";
>&2 echo "Use either 'hsort <file> [sort-options]' or 'hsort - [sort-options]'";
return 1 ;
fi
}
This is the same as Ian Sherbin answer but my implementation is :-
cut -d'|' -f3,4,7 $arg1 | uniq > filetmp.tc
head -1 filetmp.tc > file.tc;
tail -n+2 filetmp.tc | sort -t"|" -k2,2 >> file.tc;
Another simple variation on all the others, reading a file once
HEADER_LINES=2
(head -n $HEADER_LINES; sort) < data-file.dat
With Python:
import sys
HEADER_ROWS=2
for _ in range(HEADER_ROWS):
sys.stdout.write(next(sys.stdin))
for row in sorted(sys.stdin):
sys.stdout.write(row)
cat file_name.txt | sed 1d | sort
This will do what you want.