I have this function:
#! /usr/bin/env bash
function underline() {
U="${1//?/${2:--}}"
echo -e "\n$1\n${U:0:${#1}}\n"
}
underline "$1" "^-v-"
will work as expected:
$ ./u.sh "This is all you're going to see"
This is all you're going to see
^-v-^-v-^-v-^-v-^-v-^-v-^-v-^-v
It does what you expect. Originally it assumed that the underline character was just that, 1 character.
For "fun", I extended it to move from a single character underline to a repeating string underline (why? ... well ... because I can I suppose ... almost zero practical value in this exercise!).
And so, being the "let's make this so difficult that you need to write 2 pages of documentation to explain what's going on" sort of guy, I was wondering if the function could be written as a single line. And I don't mean:
function underline() { U="${1//?/${2:--}}"; echo -e "\n$1\n${U:0:${#1}}\n"; }
I don't think you can combine bash's variable search/replace with substring which is what is required.
I'm aware that this will work happily in zsh:
#! /usr/bin/env zsh
function underline() {
echo -e "\n$1\n${${1//?/${2:--}}:0:${#1}}\n"
}
underline $1 "^-v-"
e.g.
$ ./u.sh "This is all you're going to see"
This is all you're going to see
^-v-^-v-^-v-^-v-^-v-^-v-^-v-^-v
but not capable of this in bash (it seems).
No, you cannot combine those in a single parameter expansion in bash. But this single printf (a builtin in bash) should do the trick:
underline() { printf '%s\n%.*s\n' "$1" ${#1} "${1//?/${2:--}}"; }
underline "This is all you're going to see" "^-v-"
outputs
This is all you're going to see
^-v-^-v-^-v-^-v-^-v-^-v-^-v-^-v
Related
I have the following function I want to call:
function print_something {
echo "test\
something\
yep"
}
when called it prints:
'test something yep'
I would like it to print:
'testsomethingyep'
I can get this to print if I do:
function print_something {
echo "test\
something\
yep"
}
but I don't think that looks great..
(Root problem is a curl command not an echo)
Consider assembling your pieces an array, and then combining them into a string later. Array definition syntax is far more forgiving -- not requiring backslashes at all, and also allowing comments on each line and between lines.
#!/usr/bin/env bash
# ^^^^- arrays and printf -v require bash, not sh
pieces=(
test # this also lets you use comments
something # and you don't need any backslashes at all!
# one can also have a full-line comment midway through your array
"space here" # plus if you want to add a literal space you can do it
)
printf -v oneword '%s' "${pieces[#]}"
echo "$oneword"
...properly emits:
testsomethingspace here
Here are three ideas:
#!/bin/bash
print_something() {
tr -d \\n <<- EOF
test
something
yep
EOF
echo
}
print_something2() {
echo "test"$(:
)"something"$(:
)"yep"
}
print_something3() {
tr -d \\t <<- EOF
test\
something\
yep
EOF
}
print_something
print_something2
print_something3
The first uses a <<- style heredoc to remove all of the leading indentation (that indentation must be hard-tabs for this to work, and coding styles that mandate the use of spaces for indentation render this solution unusable (this is one reason coding styles that mandate the use of spaces in shell scripts are IMO utterly useless)) and the extra tr to remove the newlines. (The additional echo is then needed to add the trailing newline.). The second uses the $(:) command substitution to discard all the intervening whitespace. The 3rd manually deletes all the hard tabs.
How can I use a bashrc command like below
# .bashrc file
# google_speech
say () {
google_speech -l en "$1"
}
as a string of text, since the above code only reads out the first word of the sentence or paragraph i paste.
like for example if i go into terminal and type:
$ say hello friends how are you
then the script only thinks i typed
$ say hello
Try to use "$#" (with double quotes arround) to get all the arguments of your function:
$ declare -f mysearch # Showing the definition of mysearch (provided by your .bashrc)
mysearch ()
{
echo "Searching with keywords : $#"
}
$ mysearch foo bar # execution result
Searching with keywords : foo bar
Function or scripts arguments are like arrays, so you can use:
1) $# / ${#array[#]} to getting the number of arguments / array's elements.
2) $1 / ${array[1]} to getting the first argument / array's element.
3) $# / ${array[#]} to getting all arguments / array's elements.
EDIT: according to chepner's comment:
Using $# inside a larger string can sometimes produce unintended results. Here, the intent is to produce a single word, so it would be better to use $*
And here's a good topic with great answers explaining the differences.
EDIT 2: Do not forget to put double quotes around $# or $*, maybe your google_speach is taking only one arg. Here's a demo to give you a better understanding:
$ mysearch () { echo "Searching with keywords : $1"; }
$ mysearch2 () { mysearch "$*"; }
$ mysearch2 Hello my dear
Searching with keywords : Hello my dear
$ mysearch3 () { mysearch $*; } # missing double quotes
$ mysearch3 Hello my dear
Searching with keywords : Hello # the other arguments are at least ignored (or sometimes the program will fail when he's controlling the args).
I have a string in a shell/bash script. I want to print the string with all its "special characters" (eg. newlines, tabs, etc.) printed as literal escape sequences (eg. a newline is printed as \n, a tab is printed as \t, and so on).
(Not sure if I'm using the correct terminology; the example should hopefully clarify things.)
Example
The desired output of...
a="foo\t\tbar"
b="foo bar"
print_escape_seq "$a"
print_escape_seq "$b"
...is:
foo\t\tbar
foo\t\tbar
$a and $b are strings that were read in from a text file.
There are two tab characters between foo and bar in the $b variable.
An attempt
This is what I've tried:
#!/bin/sh
print_escape_seq() {
str=$(printf "%q\n" $1)
str=${str/\/\//\/}
echo $str
}
a="foo\t\tbar"
b="foo bar"
print_escape_seq "$a"
print_escape_seq "$b"
The output is:
foo\t\tbar
foo bar
So, it doesn't work for $b.
Is there an entirely straightforward way to accomplish this that I've missed completely?
Bash has a string quoting operation ${var#Q}
Here is some example code
bash_encode () {
esc=${1#Q}
echo "${esc:2:-1}"
}
testval=$(printf "hello\t\tworld")
set | grep "^testval="
echo "The encoded value of testval is" $(bash_encode "$testval")
Here is the output
testval=$'hello\t\tworld'
The encoded value of testval is hello\t\tworld
You will need to create a search and replace pattern for each binary value you wish to replace. Something like this:
#!/bin/bash
esc() {
# space char after //
v=${1// /\\s}
# tab character after //
v=${v// /\\t}
echo $v
}
esc "hello world"
esc "hello world"
This outputs
hello\sworld
hello\tworld
I required something similar for file paths, and I realized that ls -1b does the work, but in the research I found this solution in stackoverflow which is closer to what you were requiring.
Command to escape a string in bash
just compile it with gcc -o "escapify" escapify.c
I am having problems with expansion of command-line options containing spaces. They are not getting grouped as I expect them to be. How can I modify following code(below) to get the desired output(below).
function myFunction {
while getopts "a:b:A:" optionName; do
echo "$optionName::$OPTARG"
done
}
#dynamic variable, cannot be hardcoded into $MY_ARGS
MY_VAR="X1=162356374 X2=432876 X3=342724"
#$MY_ARGS is useful and will be used more than once,
#so we don't want to eliminate it and replace it's usage with its value everywhere
MY_ARGS="-a 24765437643 -b '$MY_VAR' -A jeeywewueuye"
myFunction $MY_ARGS
Actual Output:
a::24765437643
b::'X1=162356374
Desired Output:
a::24765437643
b::X1=162356374 X2=432876 X3=342724
A::jeeywewueuye
The best way to store a list of arguments is in an array. An array can handle arguments with whitespace without problem, and you don't have to figure out how to get the quotes and backslashes just right.
MY_ARGS=(-a 24765437643 -b "$MY_VAR" -A jeeywewueuye)
myFunction "${MY_ARGS[#]}"
The only unnatural part about arrays is the weird syntax to expand them: "${array[#]}". The quotes, curly braces, and [#] notation are all important.
I agree that arrays answer the question in the best way.
Perhaps you don't want to use arrays (colleagues will not understand), or you must obey the Google Guidelines for bash (nice work, I agree with for over 90%). that claims: "If you find you need to use arrays for anything more than assignment of ${PIPESTATUS}, you should use Python. ".
When you must look for another solutions:
An ugly solution is changing the IFS:
function myFunction {
while getopts "a:b:A:" optionName; do
echo "$optionName::$OPTARG"
done
}
#dynamic variable, cannot be hardcoded into $MY_ARGS
MY_VAR="X1=162356374 X2=432876 X3=342724"
MY_ARGS="-a/24765437643/-b/"$MY_VAR"/-A/jeeywewueuye"
IFS=/
myFunction ${MY_ARGS}
Perhaps you want to do something with myFunction
function myFunction {
while getopts "a:bA:" optionName; do
case "${optionName}" in
b) echo "${optionName}::${MY_VAR}" ;;
*) echo "${optionName}::${OPTARG}" ;;
esac
done
}
or you could tr the spaces into another character before calling myFunction and tr the characters back to spaces in myFunction().
After thoroughly searching for a way to create an associative array in bash, I found that declare -A array will do the trick. But the problem is, it is only for bash version 4 and the bash version the server has in our system is 3.2.16.
How can I achieve some sort of associative array-like hack in bash 3? The values will be passed to a script like
ARG=array[key];
./script.sh ${ARG}
EDIT: I know that I can do this in awk, or other tools but strict bash is needed for the scenario I am trying to solve.
Bash 3 has no associative arrays, so you're going to have to use some other language feature(s) for your purpose. Note that even under bash 4, the code you wrote doesn't do what you claim it does: ./script.sh ${ARG} does not pass the associative array to the child script, because ${ARG} expands to nothing when ARG is an associative array. You cannot pass an associative array to a child process, you need to encode it anyway.
You need to define some argument passing protocol between the parent script and the child script. A common one is to pass arguments in the form key=value. This assumes that the character = does not appear in keys.
You also need to figure out how to represent the associative array in the parent script and in the child script. They need not use the same representation.
A common method to represent an associative array is to use separate variables for each element, with a common naming prefix. This requires that the key name only consists of ASCII letters (of either case), digits and underscores. For example, instead of ${myarray[key]}, write ${myarray__key}. If the key is determined at run time, you need a round of expansion first: instead of ${myarray[$key]}, write
n=myarray__${key}; echo ${!n}
For an assignment, use printf -v. Note the %s format to printf to use the specified value. Do not write printf -v "myarray__${key}" %s "$value" since that would treat $value as a format and perform printf % expansion on it.
printf -v "myarray__${key}" %s "$value"
If you need to pass an associative array represented like this to a child process with the key=value argument representation, you can use ${!myarray__*} to enumerate over all the variables whose name begins with myarray__.
args=()
for k in ${!myarray__*}; do
n=$k
args+=("$k=${!n}")
done
In the child process, to convert arguments of the form key=value to separate variables with a prefix:
for x; do
if [[ $x != *=* ]]; then echo 1>&2 "KEY=VALUE expected, but got $x"; exit 120; fi
printf -v "myarray__${x%%=*}" %s "${x#*=}"
done
By the way, are you sure that this is what you need? Instead of calling a bash script from another bash script, you might want to run the child script in a subshell instead. That way it would inherit from all the variables of the parent.
Here is another post/explanation on associative arrays in bash 3 and older using parameter expansion:
https://stackoverflow.com/a/4444841
Gilles' method has a nice if statement to catch delimiter issues, sanitize oddball input ...etc. Use that.
If you are somewhat familiar with parameter expansion:
http://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html
To use in your scenario [ as stated: sending to script ]:
Script 1:
sending_array.sh
# A pretend Python dictionary with bash 3
ARRAY=( "cow:moo"
"dinosaur:roar"
"bird:chirp"
"bash:rock" )
bash ./receive_arr.sh "${ARRAY[#]}"
Script 2: receive_arr.sh
argAry1=("$#")
function process_arr () {
declare -a hash=("${!1}")
for animal in "${hash[#]}"; do
echo "Key: ${animal%%:*}"
echo "Value: ${animal#*:}"
done
}
process_arr argAry1[#]
exit 0
Method 2, sourcing the second script:
Script 1:
sending_array.sh
source ./receive_arr.sh
# A pretend Python dictionary with bash 3
ARRAY=( "cow:moo"
"dinosaur:roar"
"bird:chirp"
"bash:rock" )
process_arr ARRAY[#]
Script 2: receive_arr.sh
function process_arr () {
declare -a hash=("${!1}")
for animal in "${hash[#]}"; do
echo "Key: ${animal%%:*}"
echo "Value: ${animal#*:}"
done
}
References:
Passing arrays as parameters in bash
If you don't want to handle a lot of variables, or keys are simply invalid variable identifiers, and your array is guaranteed to have less than 256 items, you can abuse function return values. This solution does not require any subshell as the value is readily available as a variable, nor any iteration so that performance screams. Also it's very readable, almost like the Bash 4 version.
Here's the most basic version:
hash_index() {
case $1 in
'foo') return 0;;
'bar') return 1;;
'baz') return 2;;
esac
}
hash_vals=("foo_val"
"bar_val"
"baz_val");
hash_index "foo"
echo ${hash_vals[$?]}
More details and variants in this answer
You can write the key-value pairs to a file and then grep by key. If you use a pattern like
key=value
then you can egrep for ^key= which makes this pretty safe.
To "overwrite" a value, just append the new value at the end of the file and use tail -1 to get just the last result of egrep
Alternatively, you can put this information into a normal array using key=value as value for the array and then iterator over the array to find the value.
This turns out to be ridiculously easy. I had to convert a bash 4 script that used a bunch of associative arrays to bash 3. These two helper functions did it all:
array_exp() {
exp=${#//[/__}
eval "${exp//]}"
}
array_clear() {
unset $(array_exp "echo \${!$1__*}")
}
I'm flabbergasted that this actually works, but that's the beauty of bash.
E.g.
((all[ping_lo] += counts[ping_lo]))
becomes
array_exp '((all[ping_lo] += counts[ping_lo]))'
Or this print statement:
printf "%3d" ${counts[ping_lo]} >> $return
becomes
array_exp 'printf "%3d" ${counts[ping_lo]}' >> $return
The only syntax that changes is clearing. This:
counts=()
becomes
array_clear counts
and you're set. You could easily tell array_exp to recognize expressions like "=()" and handle them by rewriting them as array_clear expressions, but I prefer the simplicity of the above two functions.