I have this issue where I am doing a menu sort of program where users are supposed to type in different numbers depending on what operation(s) the want to do.
Right now I need to take in multiple flags to be placed in a command, but I can't seem to get it to work.
Catch: I cannot type in the flags directly into one variable and I will probably have to have this case list to be able to quit at will)
function fileCpy {
printf "Choices:\n1. Interactive copy, answer yes/no before doing the copy: \n2. Make backups of existing destination files\n3. Preserve file attributes\n4. Do a recursive copy\n0. Return to main menu\n"
#read choices
read $a
read $b
read $c
for choices in $choice ; do
case "$choices" in
1)
a=-i ;;
2)
b=--backup ;;
3)
c=-p ;;
#4)
#4= -R -v;;
0)
main;;
esac
echo "$a"
echo "$b"
echo "$c"
printf "\nType the name of the file you wish to copy/backup: "
read $fl1
printf "\nType the destination file: "
read $des1
cp $a $b $c $fl1 $des1
done
}
One problem is that read $a etc is wrong: you should write read a if you need the read at all. As it stands, the value read is stored in the variable with the name stored in $a.
Another problem is that it is far from clear to the innocent user that they're supposed to enter 3 lines of information before the script will continue, but the three read lines force that.
Another problem is that you don't read into $choice (via read choice) so the for loop has nothing to do.
Another problem is that your script will inherit the values of any environment variables that happen to be the same as the names of the variables you're using.
Another problem is that you don't quote the file names. It mostly won't matter unless you have a name that contains spaces or other similarly awkward characters.
A cosmetic issue is that the printf statement is ridiculously long. Use one printf per line. Or use echo. Stuff that scrolls off the RHS of the page is bad (though I don't regard 80 characters as a fixed length for lines, there's a quadratic penalty for lines that are longer than 80 — as (length-80)2 increases, the pain of the longer line goes up.
At another level altogether, the interface is modestly grotesque. As an exercise in shell scripting, it makes sense. As an exercise in how to design good shell scripts, it is a very bad design.
A design that might make sense is:
Set variables to empty: a=""; b=""; c=""; etc.
Offer a range of choices similar to those given now, but add an option to execute the command, and another to abandon ship.
Have a loop that reads choices, and sets flags.
When the user chooses execute, exit the loop and prompt for the file names.
If all's well, execute the command.
Note that you should check that the read commands work; if they don't, fail safe (don't damage anything).
Putting all those together (with some slight differences, but the same overall effect — witness the use of local for the variables):
fileCpy()
{
local a b c file dest
echo "Choices:"
echo "0. Return to main menu"
echo "1. Interactive copy, answer yes/no before doing the copy"
echo "2. Make backups of existing destination files"
echo "3. Preserve file attributes"
echo "4. Do a recursive copy"
echo "5. Execute the copy"
while printf "Your choice: " && read choice
do
[ -z "$choice" ] && return 1 # Empty input - failure
case "$choice" in
(0) return 0;;
(1) a="-i";;
(2) b="--backup";;
(3) c="-p";;
(4) d="-R";;
(5) break;;
(*) echo "Unrecognized response ($choice); please enter 0..5";;
esac
done
[ "$choice" != 5 ] && return 1 # EOF - failure
printf "Type the name of the file you wish to copy/backup: "
read file
[ -z "$file" ] && return 1 # Empty file name - failure
printf "Type the name of the destination file/directory: "
read dest
[ -z "$dest" ] && return 1 # Empty file name - failure
cp $a $b $c "$file" "$dest"
}
Test code:
echo "a=$a b=$b c=$c file=$file dest=$dest"
if fileCpy
then : OK
else echo "Failed"
fi
echo "a=$a b=$b c=$c file=$file dest=$dest"
The last block is a simple test harness. It reports on the values of the variables used inside the function, runs the function, reports if the function failed, and re-echoes the variables to demonstrate that they've not been set.
I would not use that interface unless you paid me to do so, but it more or less meets the goal of a training exercise.
if you want to do menu, you can use select construct (or case/esac). See here for info
Related
Description: I have a script that begins with a warning/question posed to user. I need the user to answe with yes/y or no/n.
Issue: Though I have a conditional to make sure the user provides one of the following answers presented above I also need to make that only ONE input is provided by the user. I have attempted using
[ "$#" -eq 1 ] or [ $# -eq 1 ] neither of these coniditionals seems to work to solve the problem
here is what I have thus far:...
#!/bin/bash
#
# Descritpion: some Windows OS script
#
#
printf "(!)WARNING(!): 1. The this program is ONLY compatible with Windows operating systems. "
printf "2. You will NEED to be logged in as an ADMIN in order to fully make use of the '*****' script.\n"
printf "Would you like to continue? yes or no (y/n): "
#would it be cleaner to use "case" rather than a "while" w/ multiple conditionals? (01.19.2020)
read opt
while (true)
do
if [ $opt == yes ] || [ $opt == y ]
then
printf "continue. \n"
break
elif [ $opt == no ] || [ $opt == n ]
then
printf "OK, exiting the script! \n"
exit 0
#elif [ "$#" -ne 1 ]
#then
# "Too many arguments have been provided, please try again. \n"
# read opt
else
printf "The opition you provided is not recognized, please try again. \n"
read opt
fi
done
Not the ideal solution, but it includes an explanation of why $# is not working as you expect:
$# returns the number of arguments passed to a function. You have read 'opt' in as a user input - not the arguments to the function.
One solution could be to wrap your infinite while loop inside a function, and then pass $opt into it. It would then be the argument(s) to your function and you could use $# to count how many there are.
For details of the workings of many built-in functions in bash, you could try:
man bash
but I accept that there is a lot of information in there. You can search for the relevant words, normally using "/{searchstring}" (but you will probably need to "escape" the special characters, in this case: "/\$\#")
Take a look at read options
read: read [-ers] [-u fd] [-t timeout] [-p prompt] [-a array] [-n nchars] [-d delim] [name ...]
One line is read from the standard input, or from file descriptor FD if the
-u option is supplied, and the first word is assigned to the first NAME,
the second word to the second NAME, and so on, with leftover words assigned
to the last NAME. Only the characters found in $IFS are recognized as word
delimiters. If no NAMEs are supplied, the line read is stored in the REPLY
variable. If the -r option is given, this signifies `raw' input, and
backslash escaping is disabled. The -d option causes read to continue
until the first character of DELIM is read, rather than newline. If the -p
option is supplied, the string PROMPT is output without a trailing newline
before attempting to read. If -a is supplied, the words read are assigned
to sequential indices of ARRAY, starting at zero. If -e is supplied and
the shell is interactive, readline is used to obtain the line. If -n is
supplied with a non-zero NCHARS argument, read returns after NCHARS
characters have been read. The -s option causes input coming from a
terminal to not be echoed.
you would be able to simplify your script using some of them.
Read the input and parse it exactly. Decide, if you want to ignore spaces or not. You could even use a regex to make the input formatted as exactly as you want.
while (true) is an unnecessary use of subshell. Just while true.
if [ $opt == yes ] will not work if opt contains whitespaces, for example user inputs y e s. It will exit with a nonzero exit status and print an error message on standard error stream. As a rule, always quote your variable expansions. Always "$opt", never $opt. This is most probably the error you are asking for fixing.
Also the == is a bash extension. Use = for string comparison.
Cosmetics: [ $opt == yes ] || [ $opt == y ] unnecessary runs two processes in case the first one fails. Just run one process [ "$opt" = yes -o "$opt" = y ]. But the first one may be just more clear.
read opt ignores leading and trailing whitespaces and removes the \ slashes. Use IFS= read -r opt to read the whole line exactly as it is.
Use shellcheck.net to check your scripts.
The $# is the number of arguments passed to the script. It is unrelated to what read does. read saves the input to the variable.
So:
while true; do
if ! IFS= read -r opt; then
echo "ERROR: END OF INPUT!" >&2
exit 2
fi
case "$opt" in
y|yes) printf 'continue. \n'; break; ;;
n|no) printf 'OK, exiting the script! \n'; exit 1; ;;
*) printf 'The opition you provided is not recognized, please try again. \n'; ;;
esac
done
I have semantic versioning for an app component and this is how I update the major version number and then store it back in version.txt. This seems like a lot of lines for a simple operation. Could someone please help me trim this down? No use of bc as the docker python image I'm on doesn't seem to have that command.
This is extracted from a yml file and version.txt only contains a major and minor number. 1.3 for example. The code below updates only the major number (1) and resets the minor number to 0. So if I ran the code on 1.3, I would get 2.
- echo $(<version.txt) 1 | awk '{print $1 + $2}' > version.txt
VERSION=$(<version.txt)
VERSION=${VERSION%.*}
echo $VERSION > version.txt
echo "New version = $(<version.txt)"
About Simplicity
"Simple" and "short" are not the same thing. echo $foo is shorter than echo "$foo", but it actually does far more things: It splits the value of foo apart on characters in IFS, evaluates each result of that split as a glob expression, and then recombines them.
Similarly, making your code simpler -- as in, limiting the number of steps in the process it goes through -- is not at all the same thing as making it shorter.
Incrementing One Piece, Leaving Others Unmodified
if IFS=. read -r major rest <version.txt || [ -n "$major" ]; then
echo "$((major + 1)).$rest" >"version.txt.$$" && mv "version.txt.$$" version.txt
else
echo "ERROR: Unable to read version number from version.txt" >&2
exit 1
fi
Incrementing Major Version, Discarding Others
if IFS=. read -r major rest <version.txt || [ -n "$major" ]; then
echo "$((major + 1))" >"version.txt.$$" && mv "version.txt.$$" "version.txt"
else
echo "ERROR: Unable to read version number from version.txt" >&2
exit 1
fi
Rationale
Both of the above are POSIX-compliant, and avoid relying on any capabilities not built into the shell.
IFS=. read -r first second third <input reads the first line of input, and splits it on .s into the shell variables first, second and third; notably, the third column in this example includes everything after the first two, so if you had a.b.c.d.e.f, you would get first=a; second=b; third=d.e.f -- hence the name rest to make this clear. See BashFAQ #1 for a detailed explanation.
$(( ... )) creates an arithmetic context in all POSIX-compliant shells. It's only useful for integer math, but since we split the pieces out with the read, we only need integer math. See http://wiki.bash-hackers.org/syntax/arith_expr
Writing to version.txt.$$ and renaming if that write is successful prevents version.txt from being left empty or corrupt if a failure takes place between the open and the write. (A version that was worried about symlink attacks would use mktemp, instead of relying on $$ to generate a unique tempfile name).
Proceeding through to the write only if the read succeeds or [ -n "$major" ] is true prevents the code from resetting the version to 1 (by adding 1 to an empty string, which evaluates in an arithmetic context as 0) if the read fails.
This question already has answers here:
How to iterate over arguments in a Bash script
(9 answers)
Closed 5 years ago.
I have this code below:
#!/bin/bash
filename=$1
file_extension=$( echo $1 | cut -d. -f2 )
directory=${filename%.*}
if [[ -z $filename ]]; then
echo "You forgot to include the file name, like this:"
echo "./convert-pdf.sh my_document.pdf"
else
if [[ $file_extension = 'pdf' ]]; then
[[ ! -d $directory ]] && mkdir $directory
convert $filename -density 300 $directory/page_%04d.jpg
else
echo "ERROR! You must use ONLY PDF files!"
fi
fi
And it is working perfectly well!
I would like to create a script which I can do something like this: ./script.sh *.pdf
How can I do it? Using asterisk.
Thank you for your time!
Firstly realize that the shell will expand *.pdf to a list of arguments. This means that your shell script will never ever see the *. Instead it will get a list of arguments.
You can use a construction like the following:
#!/bin/bash
function convert() {
local filename=$1
# do your thing here
}
if (( $# < 1 )); then
# give your error message about missing arguments
fi
while (( $# > 0 )); do
convert "$1"
shift
done
What this does is first wrap your functionality in a function called convert. Then for the main code it first checks the number of arguments passed to the script, if this is less than 1 (i.e. none) you give the error that a filename should be passed. Then you go into a while loop which is executed as long as there are arguments remaining. The first argument you pass to the convert function which does what your script already does. Then the shift operation is performed, what this does is it throws away the first argument and then shifts all the remaining arguments "left" by one place, that is what was $2 now is $1, what was $3 now is $2, etc. By doing this in the while loop until the argument list is empty you go through all the arguments.
By the way, your initial assignments have a few issues:
you can't assume that the filename has an extension, your code could match a dot in some directory path instead.
your directory assignment seems to be splitting on . instead of /
your directory assignment will contain the filename if no absolute or relative path was given, i.e. only a bare filename
...
I think you should spend a bit more time on robustness
Wrap your code in a loop. That is, instead of:
filename=$1
: code goes here
use:
for filename in "$#"; do
: put your code here
done
This question already has answers here:
Why does /bin/sh behave differently to /bin/bash even if one points to the other?
(4 answers)
Closed 7 years ago.
The main function execSteps executes emerge --pretend $package one by one, and these package's names(only names, no version information) are stored in a text file stepFile. Some of packages may have extra need for configuring package.use, package.license, this kind of extra information will be shown up after executed emerge --pretend $package. The second while loop in main function and function acceptPKGTypeItems are intended to deal with this kind of extra information.
When emerging one particular package, it may depend on a couple of more packages. For example, emerge --pretend ceph, I need to emerge more than 10 packages before ceph gets emerged. Along with Gentoo/Linux updated, new version of package may be applied. So text file stepFile only contained with package names which I need, and parsing the result of emerge --pretend $package, I'm able to get updated package emerged.
At case 0), this while loop is intended to parse the result of emerge --pretend $line(which is from stepFile), for example emerge --pretend ceph and get its dependant packages with current version, for example dev-libs/boost-1.57.0, pass it as an argument to function emgRecursion because dependant package dev-libs/boost-1.57.0 of package ceph may have its own dependant packages which are dev-libs/boost-build-1.57.0 and dev-libs/boost-1.57.0.
My problem is I get an error while : command not found in function emgRecursion when I enter 0 at case 0). Is it another different shell thing? I've added a pair parenthesis between the second while loop in main function which helped get readin answer from user for choosing package.use, package.license, or package.keywords. And I've tried to add another pair of parenthesis between the third while loop, the same problem. I've tested emgRecursion and acceptPKGTypeItems separately, both of them work fine and correctly.
Any ideas? Thank you very much.
function acceptPKGTypeItems() {
...
}
function emgRecursion() {
local output="$(emerge --pretend "="$1 | grep "\[ebuild")"
while read -r line;
do
done <<<"$output"
}
function execSteps() {
local running=0
while read -r line;
do
if (( running )); then
if [[ $line = "#"* ]] && [[ "${line/"step"}" = "$line" ]]; then
continue
else
if [[ ! "${line/"step"}" = "$line" ]]; then
echo "====== approaching to the next step which is not available at this time."
break
else
( output="$(emerge --pretend $line | grep "\[ebuild")"
echo "**************** $line is ready for emerging ****************"
while read -p "Which type of package would you like to add new item to (1-packageuse 2-packagelicense 3-packagekeywords 0-exit and continue)? " choice; do
case "$choice" in
1) echo "**************** $line is ready for emerging"
acceptPKGTypeItems $PACKAGEUSE
echo "**************** package.use has been updated."
;;
2) echo "**************** $line is ready for emerging"
acceptPKGTypeItems $PACKAGELICENSE
echo "**************** package.license has been updated."
;;
3) echo "**************** $line is ready for emerging"
acceptPKGTypeItems $PACKAGEKEYWORDS
echo "**************** package.keywords has been updated."
;;
0) echo "**************** $line starts emerging"
while read -r element;
do
local str="${element#*"] "}"
str="${str%%" "*}"
echo " $str is an element that need to be emerged. "
emgRecursion "$str"
done <<<"$output"
echo "**************** $line has been emerged. ****************"
break
;;
*) echo "~~~~~~~~~~~~~~~~ Invalid input, try again. ~~~~~~~~~~~~~~~~"
;;
esac
done) </dev/tty
fi
fi
else
[[ $line = "#"$1 ]] && running=1
done <$STEPS
}
execSteps step2
Nothing will stop while loop in main function,
output:
livecd / # ./step1
* Last emerge --sync was 32d 23h 4m 58s ago.
**************** sys-cluster/ceph is ready for emerging ****************
Which type of package would you like to add new item to (1-packageuse 2-packagelicense 3-package.keywords 0-exit and continue)?0
**************** sys-cluster/ceph starts emerging ****************
dev-libs/libaio-0.3.110 is an element that need to be emerged.
* Last emerge --sync was 32d 23h 5m 3s ago.
./step1: line 48: while: command not found
./step1: line 49: : command not found
./step1: line 50: str=dev-libs/libaio-0.3.110: No such file or directory
Take a look at what dev-libs/libaio-0.3.110 looks like.
./step1: line 77: done: command not found
sys-libs/libunwind-1.1 is an element that need to be emerged.
* Last emerge --sync was 32d 23h 5m 5s ago.
^C
Exiting on signal 2
Problem solved by copying functions other than emgRecursion to another file while I created for testing emgRecursion.
I realized that the difference between these two files(recursion for testing emgRecursion, step for test whole function) is recursion was originally created with #!/bin/bash, and step was originally a plain shell text file without any first line symbol and then I added #!/bin/bash to it. I thought there was no big difference between bash text file and shell text file in terms of syntax. In fact, THEY ARE TOTALLY DIFFERENT. If you mixed them up like my case, it's a WASTE of time.
This would be a template for your while loop. If you want to read a whole line then don't bother with putting a variable in the read line and stop useless Word splitting occurring.
while read -r; do
line=$REPLY
...
done <<<"$OUTPUT"
See Bash-Hackers
Given file socat.conf
AUTOSTART=default
SOCAT_default="TCP4-LISTEN:3724,nodelay,fork,reuseaddr,su=nobody TCP4:your.wow.server.ip.address:3724,nodelay"
The relevant part of the bash script that reads this file:
[ ! -f /etc/default/socat.conf ] || . /etc/default/socat.conf
start () {
echo "Starting $DESC:"
maxfds
umask 027
cd /tmp
if test "x$AUTOSTART" = "xnone" -o -z "x$AUTOSTART" ; then
echo "Autostart disabled."
exit 0
fi
for NAME in $AUTOSTART ; do
ARGS=`eval echo \\\$SOCAT_$NAME`
echo $ARGS
start_socat
echo " $NAME $ARGS"
done
return $?
}
For the full file see here: https://blog.bentrax.de/2009/08/26/socat-start-automatisieren-und-iptables-regeln-laden/
My question is, how can I add another command to socat.conf? I tried with
AUTOSTART=default,another
SOCAT_default="TCP4-LISTEN:3724,nodelay,fork,reuseaddr,su=nobody TCP4:your.wow.server.ip.address:3724,nodelay"
SOCAT_another="..."
However this did not work. I am not very familiar with bash scripts to understand the for NAME in $AUTOSTART loop. I think the answer lays there. Any ideas?
The for NAME in $AUTOSTART works by splitting $AUTOSTART into words using the environmental variable $IFS as delimiters (default is space, tab and newline). Each word in turn is then stored in $NAME and processed within the loop until no words remain.
The solution to your problem, then, is to separate your words using spaces (or tabs, or newlines..):
AUTOSTART="default another"
The double quotes are necessary, otherwise it will be read as two separate commands, AUTOSTART=default and another (again because of word-splitting using IFS).