I wanted to assign variable name separated by comma based on user input using function.
I will get the user input using below script and it will call function for variable assignment
while [ "$ans" != "q" ]
do
clear
echo "Choose your subject"
echo "Press q once done"
echo " 1.Science"
echo " 2.Maths"
echo " 3.English"
...
read ans
case $ans in
1) clear
Science;;
2) clear
Maths;;
3) clear
English;;
....
esac
done
clear
subjects=""
Science()
{
subjects+="$subjects Science"
}
Maths()
{
subjects+="$subjects Maths"
}
English()
{
subjects+="$subjects English"
}
At the end I wanted to have variable subjects to have option choose by the user:
Etc:
Science,Maths
Maths,English
Science,English
English
In bash, the function definition must be placed before any calls to the function.
The line subjects="" must be placed before the while loop. Otherwise its value will get lost (will be set to empty string) on exit from the loop.
The += operator causes double concatenation in the line subjects+="$subjects Science", since the right hand side contains already the expansion of the subjects variable. Either subjects="$subjects Science", or subjects+=" Science" must have been used (the same is also true for other lines in which the += operator is used). Besides, since a comma separated list is desired, a , character must be used while concatenating strings instead of space character. For example: subjects="$subjects,Science"
So a corrected script could be like this:
#!/bin/bash
subjects=""
Science() {
subjects="$subjects,Science"
}
Maths() {
subjects="$subjects,Maths"
}
English() {
subjects="$subjects,English"
}
while [ "$ans" != "q" ]; do
clear
echo "Choose your subject"
echo "Press q once done"
echo " 1.Science"
echo " 2.Maths"
echo " 3.English"
read -r ans
case $ans in
1) Science;;
2) Maths;;
3) English;;
esac
done
subjects=${subjects:1} # to remove the leading ',' character
echo "Your selections are $subjects"
Note: I wouldn't normally use a function just to append a simple string to a variable.
Related
I'm trying to combine two lists containing names (if available) and emails with a standard email text in bash (shell)
(I had to delete the irrelevant code as it contains some private info, so some of the code might look unusal.)
The first half of the code checks if there is a name list along with the email list.
The second half combines only the email address and text if no name is available, if the name list is available it also 'tries' to combine the name, email and text.
f1 = email list and f2 = name list.
As you can see in the first half of the code below, $f2 should show the names if the list is available but it does not show anything in the log file.
I been trying to sort this problem out for two days but nothing has worked. When names are available it always outputs as "Hello ..." when it should be "Hello John D..."
#FIRST HALF
if [ "$names" = "no" ]
then
text="Hello..."
elif [ "$names" = "yes" ]
then
text="Hello $f2..."
fi
#SECOND HALF
if [ "$names" = "no" ]
then
for i in $(cat $emaillist); do
echo "$text" >> /root/log
echo "$i" >> /root/log
done
elif [ "$names" = "yes" ]
then
paste $emaillist $namelist | while IFS="$(printf '\t')" read -r f1 f2
do
echo "$text" >> /root/log
echo "$f1" >> /root/log
done
fi
When you run text="Hello $f2", $f2 is looked up at the time of the assignment; an exact string is assigned to text, and only that exact string is used later, on echo "$text".
This is very desirable behavior: If shell variables' values could run arbitrary code, it would be impossible to write shell scripts that handled untrusted data safely... but it does mean that implementing your program requires some changes.
If you want to defer evaluation (looking up the value of $f2 at expansion time rather than assignment), don't use a shell variable at all: Use a function instead.
case $names in
yes) write_greeting() { echo "Hello $name..."; };;
*) write_greeting() { echo "Hello..."; };;
esac
while read -r name <&3 && read -r email <&4; do
write_greeting
echo "$email"
done 3<"$namelist" 4<"$emaillist" >>/root/log
Some enhancements in the code above:
You don't need paste to read from two streams in lockstep; you can simply open them on different file descriptors (above, FDs 3 and 4 are chosen; only 0, 1 and 2 are reserved, so larger numbers could have been selected as well) with a separate read command for each.
Opening your output sink only once for the entire loop (by putting the redirection after the done) is far more efficient than re-opening it every time you want to write a single line.
Expansions, such as "$namelist" and "$emaillist", are always quoted; this makes code more reliable if dealing with filenames with unusual characters (including spaces and glob expressions), or if IFS is at a non-default value.
I am trying to assign a variable from a prompt input choice with no luck. If the user inputs 1, I want target_db_name = "database2".
My code:
while true; do
read -p "What is the table name?" table_name
table_name=${table_name,,}
if hdfs dfs -test -e /foo/$table_name ;
then read -p "What is the target database you want to copy the
“foo.${table_name}” table to?
Your three options are:
1) database1
2) database2
3) database3
Type 1, 2, or 3: " target_db;
(((Here is where I want to state if $target_db = "1" then target_db_name
= "database1", if $target_db = "2" then target_db_name = "database2" etc...)))
read -p "Would you like to begin the HDFS copy with the following configuration:
Target Database: ${target_db_name}
Table Name: ${table_name}
Continue (Y/N):"
else echo "Please provide a valid table name.
Exiting this script" ; exit ; fi
done
I have tried creating another if statement with no luck.
"....Type 1, 2, or 3: " target_db;
else if $target_db = "1" then target_db_name = "edw_qa_history"; fi
if $target_db = "1" then won't work, because what follows if must be a command, not a test expression. Now, the most common command used in if statements is [ (yes, that's actually a command name; it's synonymous with the test command), which takes a test expression (and a close bracket) as its arguments and succeeds or fails depending on whether the expression is true or not. So the correct syntax would be something like:
if [ "$target_db" = "1" ]; then
Note that there are two other differences from what you had: I put double-quotes around the variable reference (almost always a good idea, to avoid may parsing oddities), and added a semicolon before then (needed to indicate where the arguments to [ end and shell syntax resumes). I also notice you have semicolons at the end of many lines of your script; this isn't necessary, the end-of-line is enough to indicate the end of a command. It's only if you have another command (or something like then) on the same line that you need a semicolon as a delimiter.
HOWEVER, as #Barmar pointed out in a comment, case would probably be better than a list of if and elif statements here. case is intended specifically for comparing a string against a list of other strings (or patterns), and executing different things depending on which one it matches. It looks something like this:
case "$target_db" in
1) target_db_name="database1" ;;
2) target_db_name="database2" ;;
3) target_db_name="database3" ;;
*) "Please provide a valid table name. Exiting this script" ; exit ;;
esac
Here, the double-semicolon is needed, even at the end of a line, to indicate the end of each case. Also, note that the * pattern (the last case) matches anything, so it functions like an else would in an if ... elif ... sequence.
Final note: use shellcheck.net to sanity-check your code.
You don't need an if statement to map the number to an array; you just need an array.
db_names=(
"datebase 1"
"database 2"
"database 3"
)
# ...
target_db_name=${db_names[$target_db - 1]}
if [[ -z $target_db_name ]]; then
exit
fi
I would like to find out answer on probably quite simple question: I would like to pass quoted strings with whitespaces inside as a standalone arguments for function.
There is the following file with data (for example):
one
two three
four five six
seven
And there is script with 2 simple functions:
params_checker()
{
local first_row="$1"
local second_row="$2"
local third_row="$3"
echo "Expected args are:${first_row} ; ${second_row} ; ${third_row}"
echo "All args are:"
for arg in "$#"; do
echo "${arg}"
done
}
read_from_file()
{
local args_string
while read line; do
args_string="${args_string} \"${line}\""
echo "Read row: ${line}"
done < ./test_input
params_checker ${args_string}
}
read_from_file
In other words I would like to get rows from text file as arguments to function params_checker (each row from file as different parameter, I need to keep whitespaces in the rows). Attempt to make combined string with quoted "substrings" was failed, and output was:
~/test_sh$ sh test_process.sh
Read row: one
Read row: two three
Read row: four five six
Read row: seven
Expected args are:"one" ; "two ; three"
All args are:
"one"
"two
three"
"four
five
six"
"seven"
Expectation is $1="one", $2="two three", $3="four five six" ...
Quoting of ${args_string} during passing to params_checker gave another result, string is passed as a single argument.
Could you please help to find out correct way how to pass such strings with whitespaces from file as a different standalone function argumets?
Thanks a lot for help!
In bash/ksh/zsh you'd use an array. In sh, you can use the parameters "$1", "$2" etc:
read_from_file()
{
set -- # Clear parameters
while read line; do
set -- "$#" "$line" # Append to the parameters
echo "Read row: ${line}"
done < ./test_input
params_checker "$#" # Pass all parameters
}
There you go, this should give you what you are looking for:
#!/bin/bash
params_checker()
{
local first_row="$1"
local second_row="$2"
local third_row="$3"
local forth_row="$4"
echo "Expected args are: ${first_row} ; ${second_row} ; ${third_row} ; ${forth_row}"
echo "All args are:"
for i in "$#"
do
echo "$i"
done
}
read_from_file()
{
ARRAY=()
while read line; do
echo "Read row: ${line}"
ARRAY+=("$line")
done < ./test_input
params_checker "${ARRAY[#]}"
}
read_from_file;
That should work fine in BASH. If your file is named test.sh, you can run it like this ./test.sh
I am trying to write a generic function to validate input.
Primary constraint is that an empty string is not given:
function getvalidinput(){
prompt=$1;
userinput="";
while [ "$userinput" = "" ]; do
echo $prompt;
read userinput;
done;
eval "$1=$userinput";
}
This should pass back the value by calling
somevar="Enter the value of this string var";
getvalidinput $somevar;
echo $somevar;
However firstly its only prompting the first word of the prompt and then it tries to actually execute the return sentence.
Linux fails again with a simple requirement - are there any libraries which can do trivial string functions.
Urrrggg I can believe it.
Apparently BASH has no scope.
This is horrible, however means all that is needed is
function getvalidinput(){
prompt=$1;
userinput="";
while [ "$userinput" = "" ]; do
echo $prompt;
read userinput;
done;
}
Then the caller can access with
getvalidinput "Please enter a value";
echo $userinput;
I'm a few weeks into bash scripting and I haven't advanced enough yet to get my head wrapped around this problem. Any help would be appreciated!
I have a "script.conf" file that contains the following:
key1=value1
key2=${HOME}/Folder
key3=( "k3v1" "k3 v2" "k3v3")
key4=( "k4v1"
"k4 v2"
"k4v3"
)
key5=value5
#key6="Do Not Include Me"
In a bash script, I want to read the contents of this script.conf file into an array. I've learned how to handle the scenarios for keys 1, 2, 3, and 5, but the key4 scenario throws a wrench into it with it spanning across multiple lines.
I've been exploring the use of sed -n '/=\s*[(]/,/[)]/{/' which does capture key4 and its value, but I can't figure out how to mix this so that the other keys are also captured in the matches. The range syntax is also new to me, so I haven't figured out how to separate the key/value. I feel like there is an easy regex that would accomplish what I want... in plain-text: "find and group the pattern ^(.*)= (for the key), then group everything after the '=' char until another ^(.*)= match is found, rinse and repeat". I guess if I do this, I need to change the while read line to not handle the key/value separation for me (I'll be looking into this while I'm waiting for a response). BTW, I think a solution where the value of key4 is flattened (new lines removed) would be acceptable; I know for key3 I have to store the value as a string and then convert it to an array later when I want to iterate over it since an array element apparently can't contain a list.
Am I on the right path with sed or is this a job for awk or some other tool? (I haven't ventured into awk yet). Is there an easier approach that I'm missing because I'm too deep into the forest (like changing the while read line in the LoadConfigFile function)?
Here is the code that I have so far in script.sh for processing and capturing the other pairs into the $config array:
__AppDir=$(dirname $0)
__AppName=${__ScriptName%.*}
typeset -A config #init config array
config=( #Setting Default Config values
[key1]="defaultValue1"
[key2]="${HOME}/defaultFolder"
[QuietMode]=0
[Verbose]=0 #Ex. Usage: [[ "${config[Verbose]}" -gt 0 ]] && echo ">>>Debug print"
)
function LoadConfigFile() {
local cfgFile="${1}"
shopt -s extglob #Needed to remove trailing spaces
if [ -f ${cfgFile} ]; then
while IFS='=' read -r key value; do
if [[ "${key:0:1}" == "#" ]]; then
#echo "Skipping Comment line: ${key}"
elif [ "${key:-EMPTY}" != "EMPTY" ]; then
value="${value%%\#*}" # Delete in-line, right comments
value="${value%%*( )}" # Delete trailing spaces
value="${value%%( )*}" # Delete leading spaces
#value="${value%\"*}" # Delete opening string quotes
#value="${value#\"*}" # Delete closing string quotes
#Manipulate any variables included in the value so that they can be expanded correctly
# - value must be stored in the format: "${var1}". `backticks`, "$var2", and "doubleQuotes" are left as is
value="${value//\"/\\\"}" # Escape double quotes for eval
value="${value//\`/\\\`}" # Escape backticks for eval
value="${value//\$/\\\$}" # Escape ALL '$' for eval
value="${value//\\\${/\${}" # Undo the protection of '$' if it was followed by a '{'
value=$(eval "printf '%s\n' \"${value}\"")
config[${key}]=${value} #Store the value into the config array at the specified key
echo " >>>DBG: Key = ${key}, Value = ${value}"
#else
# echo "Skipped Empty Key"
fi
done < "${cfgFile}"
fi
}
CONFIG_FILE=${__AppDir}/${__AppName}.conf
echo "Config File # ${CONFIG_FILE}"
LoadConfigFile ${CONFIG_FILE}
#Print elements of $config
echo "Script Config Values:"
echo "----------------------------"
for key in "${!config[#]}"; do #The '!' char gets an array of the keys, without it, we would get an array of the values
printf " %-20s = %s\n" "${key}" "${config[${key}]}"
done
echo "------ End Script Config ------"
#To convert to an array...
declare -a valAsArray=${config[RequiredAppPackages]} #Convert the value from a string to an array
echo "Count = ${#valAsArray[#]}"
for itemCfg in "${valAsArray[#]}"; do
echo " item = ${itemCfg}"
done
As I mentioned before, I'm just starting to learn bash and Linux scripting in general, so if you see that I'm doing some taboo things in other areas of my code too, please feel free to provide feedback in the comments... I don't want to start bad habits early on :-).
*If it matters, the OS is Ubuntu 14.04.
EDIT:
As requested, after reading the script.conf file, I would like for the elements in $config[#] to be equivalent to the following:
typeset -A config #init config array
config=(
[key1]="value1"
[key2]="${HOME}/Folder"
[key3]="( \"k3v1\" \"k3 v2\" \"k3v3\" )"
[key4]="( \"k4v1\" \"k4 v2\" \"k4v3\" )"
[key5]="value5"
)
I want to be able to convert the values of elements 'key4' and 'key3' into an array and iterated over them the same way in the following code:
declare -a keyValAsArray=${config[keyN]} #Convert the value from a string to an array
echo "Count = ${#keyValAsArray[#]}"
for item in "${keyValAsArray[#]}"; do
echo " item = ${item}"
done
I don't think it matters if \n is preserved for key4's value or not... that depends on if declare has a problem with it.
A shell is an environment from which to call tools with a language to sequence those calls. It is NOT a tool to manipulate text. The standard UNIX tool to manipulate text is awk. Trying to manipulate text in shell IS a bad habit, see why-is-using-a-shell-loop-to-process-text-considered-bad-practice for SOME of the reasons why
You still didn't post the expected result of populating the config array so I'm not sure but I think this is what you wanted:
$ cat tst.sh
declare -A config="( $(awk '
{ gsub(/^[[:space:]]+|([[:space:]]+|#.*)$/,"") }
!NF { next }
/^[^="]+=/ {
name = gensub(/=.*/,"",1)
value = gensub(/^[^=]+=/,"",1)
n2v[name] = value
next
}
{ n2v[name] = n2v[name] OFS $0 }
END {
for (name in n2v) {
value = gensub(/"/,"\\\\&","g",n2v[name])
printf "[%s]=\"%s\"\n", name, value
}
}
' script.conf
) )"
declare -p config
$ ./tst.sh
declare -A config='([key5]="value5" [key4]="( \"k4v1\" \"k4 v2\" \"k4v3\" )" [key3]="( \"k3v1\" \"k3 v2\" \"k3v3\")" [key2]="/home/Ed/Folder" [key1]="value1" )'
The above uses GNU awk for gensub(), with other awks you'd use [g]sub() instead.