I have a JSON array conf=
[ { "fraudThreshold": 4, "fraudTTLSec": 60 }, { "fraudThreshold": 44, "fraudTTLSec": 60 } ]
I want to loop through its items. So I have done the following:
for configy in $(echo "${conf}" | jq -r ".[]"); do
echo configy=$configy
done
The results are:-
configy={
configy="fraudThreshold":
configy=4,
configy="fraudTTLSec":
and so on.
It is splitting the string using spaces and giving the results one by one.
Why is bash showing this weird behavior? Is there any solution to this?
Also, it is giving proper values when I do :
configy=$(echo $conf | jq .[-1])
echo configy=$configy
Result:
configy={ "fraudThreshold": 44, "fraudTTLSec": 60 }
In order to loop through the items in the JSON array using bash, you could write:
echo "${conf}" | jq -cr ".[]" |
while read -r configy
do
echo configy="$configy"
done
This yields:
configy={"fraudThreshold":4,"fraudTTLSec":60}
configy={"fraudThreshold":44,"fraudTTLSec":60}
However there is almost surely a better way to achieve your ultimate goal.
echo "${conf}" | jq -car '.[] | "configy=" + tojson'
produces:
configy={"fraudThreshold":4,"fraudTTLSec":60}
configy={"fraudThreshold":44,"fraudTTLSec":60}
for configy in $(echo "${conf}" | jq -r ".[]"); do
It is splitting the string using spaces and giving the results one by one. Why is bash showing this weird behavior?
This behavior is not weird at all. See the Bash Reference Manual: Word Splitting:
The shell scans the results of parameter expansion, command
substitution, and arithmetic expansion that did not occur within
double quotes for word splitting.
Is there any solution to this?
Mâtt Frëëman and peak presented working solutions; you can slightly optimize them by replacing echo "${conf}" | with <<<"$conf".
Related
I have a JSON data as follows in data.json file
[
{"original_name":"pdf_convert","changed_name":"pdf_convert_1"},
{"original_name":"video_encode","changed_name":"video_encode_1"},
{"original_name":"video_transcode","changed_name":"video_transcode_1"}
]
I want to iterate through the array and extract the value for each element in a loop. I saw jq. I find it difficult to use it to iterate. How can I do that?
Just use a filter that would return each item in the array. Then loop over the results, just make sure you use the compact output option (-c) so each result is put on a single line and is treated as one item in the loop.
jq -c '.[]' input.json | while read i; do
# do stuff with $i
done
By leveraging the power of Bash arrays, you can do something like:
# read each item in the JSON array to an item in the Bash array
readarray -t my_array < <(jq --compact-output '.[]' input.json)
# iterate through the Bash array
for item in "${my_array[#]}"; do
original_name=$(jq --raw-output '.original_name' <<< "$item")
changed_name=$(jq --raw-output '.changed_name' <<< "$item")
# do your stuff
done
jq has a shell formatting option: #sh.
You can use the following to format your json data as shell parameters:
cat data.json | jq '. | map([.original_name, .changed_name])' | jq #sh
The output will look like:
"'pdf_convert' 'pdf_convert_1'"
"'video_encode' 'video_encode_1'",
"'video_transcode' 'video_transcode_1'"
To process each row, we need to do a couple of things:
Set the bash for-loop to read the entire row, rather than stopping at the first space (default behavior).
Strip the enclosing double-quotes off of each row, so each value can be passed as a parameter to the function which processes each row.
To read the entire row on each iteration of the bash for-loop, set the IFS variable, as described in this answer.
To strip off the double-quotes, we'll run it through the bash shell interpreter using xargs:
stripped=$(echo $original | xargs echo)
Putting it all together, we have:
#!/bin/bash
function processRow() {
original_name=$1
changed_name=$2
# TODO
}
IFS=$'\n' # Each iteration of the for loop should read until we find an end-of-line
for row in $(cat data.json | jq '. | map([.original_name, .changed_name])' | jq #sh)
do
# Run the row through the shell interpreter to remove enclosing double-quotes
stripped=$(echo $row | xargs echo)
# Call our function to process the row
# eval must be used to interpret the spaces in $stripped as separating arguments
eval processRow $stripped
done
unset IFS # Return IFS to its original value
From Iterate over json array of dates in bash (has whitespace)
items=$(echo "$JSON_Content" | jq -c -r '.[]')
for item in ${items[#]}; do
echo $item
# whatever you are trying to do ...
done
Try Build it around this example. (Source: Original Site)
Example:
jq '[foreach .[] as $item ([[],[]]; if $item == null then [[],.[0]] else [(.[0] + [$item]),[]] end; if $item == null then .[1] else empty end)]'
Input [1,2,3,4,null,"a","b",null]
Output [[1,2,3,4],["a","b"]]
None of the answers here worked for me, out-of-the-box.
What did work was a combination of a few:
projectList=$(echo "$projRes" | jq -c '.projects[]')
IFS=$'\n' # Read till newline
for project in ${projectList[#]}; do
projectId=$(jq '.id' <<< "$project")
projectName=$(jq -r '.name' <<< "$project")
...
done
unset IFS
NOTE: I'm not using the same data as the question does, in this example assume projRes is the output from an API that gives us a JSON list of projects, eg:
{
"projects": [
{"id":1,"name":"Project"},
... // array of projects
]
}
An earlier answer in this thread suggested using jq's foreach, but that may be much more complicated than needed, especially given the stated task. Specifically, foreach (and reduce) are intended for certain cases where you need to accumulate results.
In many cases (including some cases where eventually a reduction step is necessary), it's better to use .[] or map(_). The latter is just another way of writing [.[] | _] so if you are going to use jq, it's really useful to understand that .[] simply creates a stream of values.
For example, [1,2,3] | .[] produces a stream of the three values.
To take a simple map-reduce example, suppose you want to find the maximum length of an array of strings. One solution would be [ .[] | length] | max.
Here is a simple example that works in zch shell:
DOMAINS='["google","amazon"]'
arr=$(echo $DOMAINS | jq -c '.[]')
for d in $arr; do
printf "Here is your domain: ${d}\n"
done
I stopped using jq and started using jp, since JMESpath is the same language as used by the --query argument of my cloud service and I find it difficult to juggle both languages at once. You can quickly learn the basics of JMESpath expressions here: https://jmespath.org/tutorial.html
Since you didn't specifically ask for a jq answer but instead, an approach to iterating JSON in bash, I think it's an appropriate answer.
Style points:
I use backticks and those have fallen out of fashion. You can substitute with another command substitution operator.
I use cat to pipe the input contents into the command. Yes, you can also specify the filename as a parameter, but I find this distracting because it breaks my left-to-right reading of the sequence of operations. Of course you can update this from my style to yours.
set -u has no function in this solution, but is important if you are fiddling with bash to get something to work. The command forces you to declare variables and therefore doesn't allow you to misspell a variable name.
Here's how I do it:
#!/bin/bash
set -u
# exploit the JMESpath length() function to get a count of list elements to iterate
export COUNT=`cat data.json | jp "length( [*] )"`
# The `seq` command produces the sequence `0 1 2` for our indexes
# The $(( )) operator in bash produces an arithmetic result ($COUNT minus one)
for i in `seq 0 $((COUNT - 1))` ; do
# The list elements in JMESpath are zero-indexed
echo "Here is element $i:"
cat data.json | jp "[$i]"
# Add or replace whatever operation you like here.
done
Now, it would also be a common use case to pull the original JSON data from an online API and not from a local file. In that case, I use a slightly modified technique of caching the full result in a variable:
#!/bin/bash
set -u
# cache the JSON content in a stack variable, downloading it only once
export DATA=`api --profile foo compute instance list --query "bar"`
export COUNT=`echo "$DATA" | jp "length( [*] )"`
for i in `seq 0 $((COUNT - 1))` ; do
echo "Here is element $i:"
echo "$DATA" | jp "[$i]"
done
This second example has the added benefit that if the data is changing rapidly, you are guaranteed to have a consistent count between the elements you are iterating through, and the elements in the iterated data.
This is what I have done so far
arr=$(echo "$array" | jq -c -r '.[]')
for item in ${arr[#]}; do
original_name=$(echo $item | jq -r '.original_name')
changed_name=$(echo $item | jq -r '.changed_name')
echo $original_name $changed_name
done
I am trying to use jq to parse information from the TVDB api. I need to pull a couple of fields and assign the values to variables that I can continue to use in my bash script. I know I can easily assign the output to one variable through bash with variable="$(command)" but I need the output to produce multiple variables and I don't want to make to use multiple commands.
I read this documentation:
https://stedolan.github.io/jq/manual/v1.5/#Advancedfeatures
but I don't know if this relevant to what I am trying to do.
jq '.data' produces the following output:
[
{
"absoluteNumber": 51,
"airedEpisodeNumber": 6,
"airedSeason": 4,
"airedSeasonID": 680431,
"dvdEpisodeNumber": 6,
"dvdSeason": 4,
"episodeName": "We Will Rise",
"firstAired": "2017-03-15",
"id": 5939660,
"language": {
"episodeName": "en",
"overview": "en"
},
"lastUpdated": 1490769062,
"overview": "Clarke and Roan must work together in hostile territory in order to deliver an invaluable asset to Abby and her team."
}
]
I tried jq '.data | {episodeName:$name}' and jq '.data | .episodeName as $name' just to try and get one working. I don't understand the documentation or even if it's what I'm looking for. Is there a way to do what I am trying to do?
You can use separate variables with read :
read var1 var2 var3 < <(echo $(curl -s 'https://api.github.com/repos/torvalds/linux' |
jq -r '.id, .name, .full_name'))
echo "id : $var1"
echo "name : $var2"
echo "full_name : $var3"
Using array :
read -a arr < <(echo $(curl -s 'https://api.github.com/repos/torvalds/linux' |
jq -r '.id, .name, .full_name'))
echo "id : ${arr[0]}"
echo "name : ${arr[1]}"
echo "full_name : ${arr[2]}"
Also you can split jq output with some character :
IFS='|' read var1 var2 var3 var4 < <(curl '......' | jq -r '.data |
map([.absoluteNumber, .airedEpisodeNumber, .episodeName, .overview] |
join("|")) | join("\n")')
Or use an array like :
set -f; IFS='|' data=($(curl '......' | jq -r '.data |
map([.absoluteNumber, .airedEpisodeNumber, .episodeName, .overview] |
join("|")) | join("\n")')); set +f
absoluteNumber, airedEpisodeNumber, episodeName & overview are respectively ${data[0]}, ${data[1]}, ${data[2]}, ${data[3]}. set -f and set +f are used to respectively disable & enable globbing.
For the jq part, all your required fields are mapped and delimited with a '|' character with join("|")
If your are using jq < 1.5, you'll have to convert Number to String with tostring for each Number fields eg:
IFS='|' read var1 var2 var3 var4 < <(curl '......' | jq -r '.data |
map([.absoluteNumber|tostring, .airedEpisodeNumber|tostring, .episodeName, .overview] |
join("|")) | join("\n")')
jq always produces a stream of zero or more values. For example, to produce the two values corresponding to "episodeName" and "id"' you could write:
.data[] | ( .episodeName, .id )
For your purposes, it might be helpful to use the -c command-line option, to ensure each JSON output value is presented on a single line. You might also want to use the -r command-line option, which removes the outermost quotation marks from each output value that is a JSON string.
For further variations, please see the jq FAQ https://github.com/stedolan/jq/wiki/FAQ, e.g. the question:
Q: How can a stream of JSON texts produced by jq be converted into a bash array of corresponding values?
Experimental conversion of quoted OP input, (tv.dat), to a series of bash variables, (and an array). The jq code is mostly borrowed from here and there, but I don't know how to get jq to unroll an array within an array, so the sed code does that, (that's only good for one level, but so are bash arrays):
jq -r ".[] | to_entries | map(\"DAT_\(.key) \(.value|tostring)\") | .[]" tv.dat |
while read a b ; do echo "${a,,}='$b'" ; done |
sed -e '/{.*}/s/"\([^"]*\)":/[\1]=/g;y/{},/() /' -e "s/='(/=(/;s/)'$/)/"
Output:
dat_absolutenumber='51'
dat_airedepisodenumber='6'
dat_airedseason='4'
dat_airedseasonid='680431'
dat_dvdepisodenumber='6'
dat_dvdseason='4'
dat_episodename='We Will Rise'
dat_firstaired='2017-03-15'
dat_id='5939660'
dat_language=([episodeName]="en" [overview]="en")
dat_lastupdated='1490769062'
dat_overview='Clarke and Roan must work together in hostile territory in order to deliver an invaluable asset to Abby and her team.'
I would like to convert a list into JSON array. I'm looking at jq for this but the examples are mostly about parsing JSON (not creating it). It would be nice to know proper escaping will occur. My list is single line elements so the new line will probably be the best delimiter.
I was also trying to convert a bunch of lines into a JSON array, and was at a standstill until I realized that -s was the only way I could handle more than one line at a time in the jq expression, even if that meant I'd have to parse the newlines manually.
jq -R -s -c 'split("\n")' < just_lines.txt
-R to read raw input
-s to read all input as a single string
-c to not pretty print the output
Easy peasy.
Edit: I'm on jq ≥ 1.4, which is apparently when the split built-in was introduced.
--raw-input, then --slurp
Just summarizing what the others have said in a hopefully quicker to understand form:
cat /etc/hosts | jq --raw-input . | jq --slurp .
will return you:
[
"fe00::0 ip6-localnet",
"ff00::0 ip6-mcastprefix",
"ff02::1 ip6-allnodes",
"ff02::2 ip6-allrouters"
]
Explanation
--raw-input/-R:
Don´t parse the input as JSON. Instead, each line of text is passed
to the filter as a string. If combined with --slurp, then the
entire input is passed to the filter as a single long string.
--slurp/-s:
Instead of running the filter for each JSON object in the input,
read the entire input stream into a large array and run the filter
just once.
You can also use jq -R . to format each line as a JSON string and then jq -s (--slurp) to create an array for the input lines after parsing them as JSON:
$ printf %s\\n aa bb|jq -R .|jq -s .
[
"aa",
"bb"
]
The method in chbrown's answer adds an empty element to the end if the input ends with a linefeed, but you can use printf %s "$(cat)" to remove trailing linefeeds:
$ printf %s\\n aa bb|jq -R -s 'split("\n")'
[
"aa",
"bb",
""
]
$ printf %s\\n aa bb|printf %s "$(cat)"|jq -R -s 'split("\n")'
[
"aa",
"bb"
]
If the input lines don't contain ASCII control characters (which have to be escaped in strings in valid JSON), you can use sed:
$ printf %s\\n aa bb|sed 's/["\]/\\&/g;s/.*/"&"/;1s/^/[/;$s/$/]/;$!s/$/,/'
["aa",
"bb"]
Update: If your jq has inputs you can simply write:
jq -nR [inputs] /etc/hosts
to produce a JSON array of strings. This avoids having to read the text file as a whole.
I found in the man page for jq and through experimentation what seems to me to be a simpler answer.
$ cat test_file.txt | jq -Rsc '. / "\n" - [""]'
["aa","bb"]
The -R is to read without trying to parse json, the -s says to read all of the input as one string, and the -c is for one-line output - not necessary, but it's what I was looking for.
Then in the string I pass to jq, the '.' says take the input as it is. The '/ \n' says to divide the string (split it) on newlines. The '- [""]' says to remove from the resulting array any empty strings (resulting from an extra newline at the end).
It's one line and without any complicated constructs, using just simple built in jq features.
Im trying to make a script that takes a .txt file containing lines
like:
davda103:David:Davidsson:800104-1234:TNCCC_1:TDDB46 TDDB80:
and then sort them etc. Thats just the background my problem lies here:
#!/bin/sh -x
cat $1 |
while read a
do
testsak = `echo $a | cut -f 1 -d :`; <---**
echo $testsak;
done
Where the arrow is, when I try to run this code I get some kind of weird error.
+ read a
+ cut -f+ echo 1 -d :davda103:David:Davidsson:800104-1234:TNCCC_1:TDDB46
TDDB80:
+ testsak = davda103
scriptTest.sh: testsak: Det går inte att hitta
+ echo
(I have my linux in swedish because school -.-) Anyways that error just says that it cant find... something. Any ideas what could be causing my problem?
You have extra spaces around the assignment operator, remove them:
testsak=`echo $a | cut -f 1 -d :`; <---**
The spaces around the equal sign
testsak = `echo $a | cut -f 1 -d :`; <---**
causes bash to interpret this as a command testak with arguments = and the result of the command substitution. Removing the spaces will fix the immediate error.
A much more efficient way to extract the value from a is to let read do it (and use input redirection instead of cat):
while IFS=: read testak the_rest; do
echo $testak
done < "$1"
I'm have a bash script that I use to manipulate files on a computation cluster.
The files I am trying to manipulate are of the format:
beadSize=6.25
minBoxSize=2.2
lipids=1200
chargedLipids=60
cations=0
HEAD=0
CHEAD=-2
BODY=2
TAIL=3
ION=-1
RHO_BODY=10
RHO_TAIL=14
tol=1e-10
lb=7.1
FTsize=8
ROUNDS=1000000
ftROUNDS=10
wROUNDS=1000
dt=0.01
alpha=1
transSize=0.15
transSizeZ=0.0
ionsTransSize=2.8
ionsTransSizeZ=2.8
rotateSize=0.18
volSize=8
modSize=0.0
forceFactor=2
kappaCV=0
sysSize=26
zSize=300
iVal=1
split=0
randSeed=580
I call a function inside a loop:
for per in $(seq 70 -5 5); do
for seed in {580..583}; do
for c in {"fs","fd","bfs","bfd"}; do
let count=$count+1
startJob $per $seed $c $count
done
done
done
and the lines I use to manipulate:
let n=$1*12
echo $n
cat trm.dat | sed '/memFile*/d' | sed '/rStart*/d' | sed '/test*/d'| sed 's/modSize=[0-9.]*/modSize=0.0/' | sed 's/chachargedLipids=[0-9]*/chargedLipids="$n"/' | grep char #> propFile.dat
for $per=15, for example, I expect $n==180. However when I run the script I see:
180
chargedLipids=120
What am I doing wrong?
Note
I have also tried to use:
sed "s/chachargedLipids=[0-9]*/chargedLipids=$n/"
With the same result.
chacharged != charged, and the final sed is doing nothing. With single quotes, you would expect to see the literal text chargedLipids="$n" in your output if a replacement was being made.