I am looking to create a shell script that reads command line arguments, then concatenates the contents of those files and print it to stdout. I need to verify the files passed to the command line exist.
I have written some code so far, but the script only works if only one command line argument is passed. If passing more than one argument, the error checking I have tried does not work.
#!/bin/bash
if [ $# -eq 0 ]; then
echo -e "Usage: concat FILE ... \nDescription: Concatenates FILE(s)
to standard output separating them with divider -----."
exit 1
fi
for var in "$#"
do
if [[ ! -e $# ]]; then
echo "One or more files does not exist"
exit 1
fi
done
for var in "$#"
do
if [ -f $var ]; then
cat $var
echo "-----"
exit 0
fi
done
I need to fix the error checking on this so that every command line argument is checked to be an existing file. If a file does not exist, the error must be printed to stderr and nothing should be printed to stdout.
You have a bug in line 11:
if [[ ! -e $# ]]; then
You do need to check for a given file here using $var like that:
if [[ ! -e "$var" ]]; then
And you exit prematurely in line 23 - you will always print only a
single file. And remember to always quote your variable because
otherwise your script would not run correctly on files that have a whitespaces in the name, for example:
$ echo a line > 'a b'
$ cat 'a b'
a line
$ ./concat.sh 'a b'
cat: a: No such file or directory
cat: b: No such file or directory
-----.
You said:
if a file does not exist, the error must be printed to stderr and
nothing should be printed to stdout.
You aren't printing anything to stderr at the moment, if you want to
you should do:
echo ... >&2
And you should use printf instead of echo as it's more portable
even though you're using Bash.
All in all, your script could look like this:
#!/bin/bash
if [ $# -eq 0 ]; then
printf "Usage: concat FILE ... \nDescription: Concatenates FILE(s) to standard output separating them with divider -----.\n" >&2
exit 1
fi
for var in "$#"
do
if [[ ! -e "$var" ]]; then
printf "One or more files does not exist\n" >&2
exit 1
fi
done
for var in "$#"
do
if [ -f "$var" ]; then
cat "$var"
printf -- "-----\n"
fi
done
exit 0
I am trying to check if a user types multiple arguments in a command line using case and if/else statements. What's wrong is that I keep getting the default case instead of the same command, but with 2 more arguments. For instance, one of my conditions is:
del)
if [ -z "$2" ] || [ -z "$3" ]
then
echo "Usage: removes a file"
else
echo "using Bash command: rm $2 $3"
rm $2 $3
echo done
fi
prints the first condition, but if I type, say, del aaa bbb, I get the default case, which is:
echo "ERROR: Unrecognized command"
I'm also using this to read a user's input, if that helps.
read -p "wcl> " -r wcl $2 $3
I don't really know if there's a better way to solve this without scrapping all my code and starting from scratch.
This is the full code:
#!/bin/bash
#use read command
echo Welcome to the Windows Command Line simulator!
echo Enter your commands below
while true
do
read -p "wcl> " -r wcl $2 $3
case $wcl in
dir)
echo "using Bash command: ls $2 $3"
ls
continue
;;
copy)
FILE="$2"
if [ "$#" -ne 3 ]
then
echo "Usage: copy sourcefile destinationfile"
else
echo "using Bash command: cp $2 $3"
if [ -f "$FILE" ]
then
cp $2 $3
else
echo "cannot stat $FILE: No such file or directory">&2
fi
echo done
fi
continue
;;
del)
if [ -z "$2" ] || [ -z "$3" ]
then
echo "Usage: removes a file"
else
echo "using Bash command: rm $2 $3"
rm $2 $3
echo done
fi
continue
;;
move)
if [ -z "$2" ] || [ -z "$3" ]
then
echo "Usage: moves a file to another file name and location"
else
echo "using Bash command: mv $2 $3"
mv $2 $3
echo done
fi
continue
;;
rename)
if [ -z "$2" ] || [ -z "$3" ]
then
echo "Usage: renames a file"
else
echo "using Bash command: mv $2 $3"
mv $2 $3
echo done
fi
continue
;;
ipconfig)
ifconfig eth0 | grep "inet addr" | cut -d ':' -f 2 | cut -d ' ' -f 1
continue
;;
exit)
echo "Goodbye"
exit 1
;;
^c)
echo "Goodbye"
exit 1
;;
*)
echo "ERROR: Unrecognized command"
continue
esac
done
You can't use read to set the positional parameters, although it isn't clear why you would need to here. Just use regular parameters.
while true
do
read -p "wcl> " -r wcl arg1 arg2
case $wcl in
dir)
echo "using Bash command: ls $arg1 $arg2"
ls "$arg1" "$arg2"
continue
;;
# ...
esac
done
The way read -r wcl $2 $3 is executed is that $2 and $3 are first expanded to give names that read will use to set variables. If those aren't set, then the command reduces to read -r wcl, and so your entire command line is assigned to the variable wcl, not just the command.
However, read by itself is not going to do the same parsing that the shell already does, if you goal is to write your own shell.
If you are really using bash, you can insert the words you read into positional parameters through an array. (You could also just leave them in the array, but the syntax for referring to positional parameters is simpler.)
# -a: read the successive words into an array
read -r -p "wcl> " -a params
# set the positional parameters to the expansion of the array
set -- "${params[#]}"
wcl=$1 # Or you could do the case on "$1"
This will also set $# to the number of words read, as a side-effect of setting the positional parameters.
As #chepner points outs, the read is problematic: It simply splits the input into whitespace-separated words, without respecting quotes, backslashes, and whatever other shell metacharacters you might want to implement. Doing a full bash-style parse of a command-line in bash itself would be quite a difficult exercise.
I am looking into how a particular exploit works, and I chose to look at one in the program 'chkrootkit' which allows for any user to run a malicious file as root. The source code for this vulnerable shellscript is as follows
slapper (){
SLAPPER_FILES="${ROOTDIR}tmp/.bugtraq ${ROOTDIR}tmp/.bugtraq.c"
SLAPPER_FILES="$SLAPPER_FILES ${ROOTDIR}tmp/.unlock ${ROOTDIR}tmp/httpd \
${ROOTDIR}tmp/update ${ROOTDIR}tmp/.cinik ${ROOTDIR}tmp/.b"a
SLAPPER_PORT="0.0:2002 |0.0:4156 |0.0:1978 |0.0:1812 |0.0:2015 "
OPT=-an
STATUS=0
file_port=
if ${netstat} "${OPT}"|${egrep} "^tcp"|${egrep} "${SLAPPER_PORT}">
/dev/null 2>&1
then
STATUS=1
[ "$SYSTEM" = "Linux" ] && file_port=`netstat -p ${OPT} | \
$egrep ^tcp|$egrep "${SLAPPER_PORT}" | ${awk} '{ print $7 }' |
tr -d :`
fi
for i in ${SLAPPER_FILES}; do
if [ -f ${i} ]; then
file_port=$file_port $i
STATUS=1
fi
done
if [ ${STATUS} -eq 1 ] ;then
echo "Warning: Possible Slapper Worm installed ($file_port)"
else
if [ "${QUIET}" != "t" ]; then echo "not infected"; fi
return ${NOT_INFECTED}
fi
}
I know that the reason the exploit works is because the line 'file_port=$file_port $i' will execute all files specified in $SLAPPER_FILES as the user chkrootkit is running (usually root), if $file_port is empty, because of missing quotation marks around the
variable assignment."
My question is why does the command
file_port=$file_port $i
result in execution of the file? Assuming that $i refers to the path of the file (/tmp/update)
I can see that file_port might be changed to some long netstat command in the previous if statement, is this something to do with it?
I've been trying to get my head around this all day to no avail, so at this point any help will be greatly appreciated :)
This is the one-shot variable assignment feature of any Bourne shell. Any command can be prefixed with zero or more variable assignments:
VAR1=VALUE1 VAR2=VALUE2 command arguments ...
Runs command arguments ... with the respective environment variables set for just this command. A typical use might be
EDITOR=vim crontab -e
I have to write a script in linux that saves one line of text to a file and then appends a new line. What I currently have is something like:
read "This line will be saved to text." Text1
$Text1 > $Script.txt
read "This line will be appended to text." Text2
$Text2 >> $Script.txt
One of the main benefits of scripting is that you can automate processes. Using
read like you have destroys that. You can accept input from the user without
losing automation:
#!/bin/sh
if [ "$#" != 3 ]
then
echo 'script.sh [Text1] [Text2] [Script]'
exit
fi
printf '%s\n' "$1" "$2" > "$3"
Assuming you don't mind if the second line of your output file is overwritten (not appended) every time the script is run; this might do.
#!/bin/sh
output_file=output.dat
if [ -z "$1" ] || [ -z "$2" ]; then echo Need at least two arguments.; fi
line1=$1; line2=$2
echo $line1 > $output_file
echo $line2 >> $output_file
Executing the script:
# chmod +x foo.sh
# ./foo.sh
Need at least two arguments.
# ./foo.sh hello world
# cat output.dat
hello
world
How can I determine the name of the Bash script file inside the script itself?
Like if my script is in file runme.sh, then how would I make it to display "You are running runme.sh" message without hardcoding that?
me=`basename "$0"`
For reading through a symlink1, which is usually not what you want (you usually don't want to confuse the user this way), try:
me="$(basename "$(test -L "$0" && readlink "$0" || echo "$0")")"
IMO, that'll produce confusing output. "I ran foo.sh, but it's saying I'm running bar.sh!? Must be a bug!" Besides, one of the purposes of having differently-named symlinks is to provide different functionality based on the name it's called as (think gzip and gunzip on some platforms).
1 That is, to resolve symlinks such that when the user executes foo.sh which is actually a symlink to bar.sh, you wish to use the resolved name bar.sh rather than foo.sh.
# ------------- SCRIPT ------------- #
#!/bin/bash
echo
echo "# arguments called with ----> ${#} "
echo "# \$1 ----------------------> $1 "
echo "# \$2 ----------------------> $2 "
echo "# path to me ---------------> ${0} "
echo "# parent path --------------> ${0%/*} "
echo "# my name ------------------> ${0##*/} "
echo
exit
# ------------- CALLED ------------- #
# Notice on the next line, the first argument is called within double,
# and single quotes, since it contains two words
$ /misc/shell_scripts/check_root/show_parms.sh "'hello there'" "'william'"
# ------------- RESULTS ------------- #
# arguments called with ---> 'hello there' 'william'
# $1 ----------------------> 'hello there'
# $2 ----------------------> 'william'
# path to me --------------> /misc/shell_scripts/check_root/show_parms.sh
# parent path -------------> /misc/shell_scripts/check_root
# my name -----------------> show_parms.sh
# ------------- END ------------- #
With bash >= 3 the following works:
$ ./s
0 is: ./s
BASH_SOURCE is: ./s
$ . ./s
0 is: bash
BASH_SOURCE is: ./s
$ cat s
#!/bin/bash
printf '$0 is: %s\n$BASH_SOURCE is: %s\n' "$0" "$BASH_SOURCE"
$BASH_SOURCE gives the correct answer when sourcing the script.
This however includes the path so to get the scripts filename only, use:
$(basename $BASH_SOURCE)
If the script name has spaces in it, a more robust way is to use "$0" or "$(basename "$0")" - or on MacOS: "$(basename \"$0\")". This prevents the name from getting mangled or interpreted in any way. In general, it is good practice to always double-quote variable names in the shell.
If you want it without the path then you would use ${0##*/}
To answer Chris Conway, on Linux (at least) you would do this:
echo $(basename $(readlink -nf $0))
readlink prints out the value of a symbolic link. If it isn't a symbolic link, it prints the file name. -n tells it to not print a newline. -f tells it to follow the link completely (if a symbolic link was a link to another link, it would resolve that one as well).
I've found this line to always work, regardless of whether the file is being sourced or run as a script.
echo "${BASH_SOURCE[${#BASH_SOURCE[#]} - 1]}"
If you want to follow symlinks use readlink on the path you get above, recursively or non-recursively.
The reason the one-liner works is explained by the use of the BASH_SOURCE environment variable and its associate FUNCNAME.
BASH_SOURCE
An array variable whose members are the source filenames where the corresponding shell function names in the FUNCNAME array variable are defined. The shell function ${FUNCNAME[$i]} is defined in the file ${BASH_SOURCE[$i]} and called from ${BASH_SOURCE[$i+1]}.
FUNCNAME
An array variable containing the names of all shell functions currently in the execution call stack. The element with index 0 is the name of any currently-executing shell function. The bottom-most element (the one with the highest index) is "main". This variable exists only when a shell function is executing. Assignments to FUNCNAME have no effect and return an error status. If FUNCNAME is unset, it loses its special properties, even if it is subsequently reset.
This variable can be used with BASH_LINENO and BASH_SOURCE. Each element of FUNCNAME has corresponding elements in BASH_LINENO and BASH_SOURCE to describe the call stack. For instance, ${FUNCNAME[$i]} was called from the file ${BASH_SOURCE[$i+1]} at line number ${BASH_LINENO[$i]}. The caller builtin displays the current call stack using this information.
[Source: Bash manual]
Since some comments asked about the filename without extension, here's an example how to accomplish that:
FileName=${0##*/}
FileNameWithoutExtension=${FileName%.*}
Enjoy!
These answers are correct for the cases they state but there is a still a problem if you run the script from another script using the 'source' keyword (so that it runs in the same shell). In this case, you get the $0 of the calling script. And in this case, I don't think it is possible to get the name of the script itself.
This is an edge case and should not be taken TOO seriously. If you run the script from another script directly (without 'source'), using $0 will work.
Re: Tanktalus's (accepted) answer above, a slightly cleaner way is to use:
me=$(readlink --canonicalize --no-newline $0)
If your script has been sourced from another bash script, you can use:
me=$(readlink --canonicalize --no-newline $BASH_SOURCE)
I agree that it would be confusing to dereference symlinks if your objective is to provide feedback to the user, but there are occasions when you do need to get the canonical name to a script or other file, and this is the best way, imo.
this="$(dirname "$(realpath "$BASH_SOURCE")")"
This resolves symbolic links (realpath does that), handles spaces (double quotes do this), and will find the current script name even when sourced (. ./myscript) or called by other scripts ($BASH_SOURCE handles that). After all that, it is good to save this in a environment variable for re-use or for easy copy elsewhere (this=)...
You can use $0 to determine your script name (with full path) - to get the script name only you can trim that variable with
basename $0
if your invoke shell script like
/home/mike/runme.sh
$0 is full name
/home/mike/runme.sh
basename $0 will get the base file name
runme.sh
and you need to put this basic name into a variable like
filename=$(basename $0)
and add your additional text
echo "You are running $filename"
so your scripts like
/home/mike/runme.sh
#!/bin/bash
filename=$(basename $0)
echo "You are running $filename"
This works fine with ./self.sh, ~/self.sh, source self.sh, source ~/self.sh:
#!/usr/bin/env bash
self=$(readlink -f "${BASH_SOURCE[0]}")
basename=$(basename "$self")
echo "$self"
echo "$basename"
Credits: I combined multiple answers to get this one.
echo "$(basename "`test -L ${BASH_SOURCE[0]} \
&& readlink ${BASH_SOURCE[0]} \
|| echo ${BASH_SOURCE[0]}`")"
In bash you can get the script file name using $0. Generally $1, $2 etc are to access CLI arguments. Similarly $0 is to access the name which triggers the script(script file name).
#!/bin/bash
echo "You are running $0"
...
...
If you invoke the script with path like /path/to/script.sh then $0 also will give the filename with path. In that case need to use $(basename $0) to get only script file name.
Short, clear and simple, in my_script.sh
#!/bin/bash
running_file_name=$(basename "$0")
echo "You are running '$running_file_name' file."
Out put:
./my_script.sh
You are running 'my_script.sh' file.
Info thanks to Bill Hernandez. I added some preferences I'm adopting.
#!/bin/bash
function Usage(){
echo " Usage: show_parameters [ arg1 ][ arg2 ]"
}
[[ ${#2} -eq 0 ]] && Usage || {
echo
echo "# arguments called with ----> ${#} "
echo "# \$1 -----------------------> $1 "
echo "# \$2 -----------------------> $2 "
echo "# path to me ---------------> ${0} " | sed "s/$USER/\$USER/g"
echo "# parent path --------------> ${0%/*} " | sed "s/$USER/\$USER/g"
echo "# my name ------------------> ${0##*/} "
echo
}
Cheers
DIRECTORY=$(cd `dirname $0` && pwd)
I got the above from another Stack Overflow question, Can a Bash script tell what directory it's stored in?, but I think it's useful for this topic as well.
Here is what I came up with, inspired by Dimitre Radoulov's answer (which I upvoted, by the way).
script="$BASH_SOURCE"
[ -z "$BASH_SOURCE" ] && script="$0"
echo "Called $script with $# argument(s)"
regardless of the way you call your script
. path/to/script.sh
or
./path/to/script.sh
$0 will give the name of the script you are running. Create a script file and add following code
#!/bin/bash
echo "Name of the file is $0"
then run from terminal like this
./file_name.sh
To get the "realpath" of script or sourced scripts in all cases :
fullname=$(readlink $0) # Take care of symbolic links
dirname=${fullname%/*} # Get (most of the time) the dirname
realpath=$(dirname $BASH_SOURCE) # TO handle sourced scripts
[ "$realpath" = '.' ] && realpath=${dirname:-.}
Here is the bash script to generate (in a newly created "workdir" subdir and in "mytest" in current dir), a bash script which in turn will source another script, which in turm will call a bash defined function .... tested with many ways to launch them :
#!/bin/bash
##############################################################
ret=0
fullname=$(readlink $0) # Take care of symbolic links
dirname=${fullname%/*} # Get (most of the time) the dirname
realpath=$(dirname $BASH_SOURCE) # TO handle sourced scripts
[ "$realpath" = '.' ] && realpath=${dirname:-.}
fullname_withoutextension=${fullname%.*}
mkdir -p workdir
cat <<'EOD' > workdir/_script_.sh
#!/bin/bash
##############################################################
ret=0
fullname=$(readlink $0) # Take care of symbolic links
dirname=${fullname%/*} # Get (most of the time) the dirname
realpath=$(dirname $BASH_SOURCE) # TO handle sourced scripts
[ "$realpath" = '.' ] && realpath=${dirname:-.}
fullname_withoutextension=${fullname%.*}
echo
echo "# ------------- RESULTS ------------- #"
echo "# path to me (\$0)-----------> ${0} "
echo "# arguments called with ----> ${#} "
echo "# \$1 -----------------------> $1 "
echo "# \$2 -----------------------> $2 "
echo "# path to me (\$fullname)----> ${fullname} "
echo "# parent path(\${0%/*})------> ${0%/*} "
echo "# parent path(\$dirname)-----> ${dirname} "
echo "# my name ----\${0##*/}------> ${0##*/} "
echo "# my source -\${BASH_SOURCE}-> ${BASH_SOURCE} "
echo "# parent path(from BASH_SOURCE) -> $(dirname $BASH_SOURCE)"
echo "# my function name -\${FUNCNAME[0]}------> ${FUNCNAME[0]}"
echo "# my source or script real path (realpath)------------------> $realpath"
echo
[ "$realpath" = "workdir" ] || ret=1
[ $ret = 0 ] || echo "*******************************************************"
[ $ret = 0 ] || echo "*********** ERROR **********************************"
[ $ret = 0 ] || echo "*******************************************************"
show_params () {
echo
echo "# --- RESULTS FROM show_params() ---- #"
echo "# path to me (\$0)-----------> ${0} "
echo "# arguments called with ----> ${#} "
echo "# \$1 -----------------------> $1 "
echo "# \$2 -----------------------> $2 "
echo "# path to me (\$fullname)----> ${fullname} "
echo "# parent path(\${0%/*})------> ${0%/*} "
echo "# parent path(\$dirname)-----> ${dirname} "
echo "# my name ----\${0##*/}------> ${0##*/} "
echo "# my source -\${BASH_SOURCE}-> ${BASH_SOURCE} "
echo "# parent path(from BASH_SOURCE) -> $(dirname $BASH_SOURCE)"
echo "# my function name -\${FUNCNAME[0]}------> ${FUNCNAME[0]}"
echo "# my source or script real path (realpath)------------------> $realpath"
echo
[ "$realpath" = "workdir" ] || ret=1
[ $ret = 0 ] || echo "*******************************************************"
[ $ret = 0 ] || echo "*********** ERROR **********************************"
[ $ret = 0 ] || echo "*******************************************************"
}
show_params "$#"
EOD
cat workdir/_script_.sh > workdir/_side_by_side_script_sourced.inc
cat <<'EOD' >> workdir/_script_.sh
echo "# . $realpath/_side_by_side_script_sourced.inc 'hello there' 'william'"
. $realpath/_side_by_side_script_sourced.inc 'hello there' 'william'
[ $ret = 0 ] || echo "*******************************************************"
[ $ret = 0 ] || echo "*********** ERROR **********************************"
[ $ret = 0 ] || echo "*******************************************************"
EOD
chmod +x workdir/_script_.sh
[ -L _mytest_ ] && rm _mytest_
ln -s workdir/_script_.sh _mytest_
# ------------- CALLED ------------- #
called_by () {
echo '=========================================================================='
echo " Called by : " "$#"
echo '=========================================================================='
eval "$#"
}
called_by bash _mytest_
called_by ./_mytest_
called_by bash workdir/_script_.sh
called_by workdir/_script_.sh
called_by . workdir/_script_.sh
# ------------- RESULTS ------------- #
echo
echo
[ $ret = 0 ] || echo "*******************************************************"
[ $ret = 0 ] || echo "*********** ERROR **********************************"
[ $ret = 0 ] || echo "*******************************************************"
echo
[ $ret = 0 ] && echo ".... location of scripts (\$realpath) should always be equal to $realpath, for all test cases at date".
echo
# ------------- END ------------- #
echo "You are running $0"
somthing like this?
export LC_ALL=en_US.UTF-8
#!/bin/bash
#!/bin/sh
#----------------------------------------------------------------------
start_trash(){
ver="htrash.sh v0.0.4"
$TRASH_DIR # url to trash $MY_USER
$TRASH_SIZE # Show Trash Folder Size
echo "Would you like to empty Trash [y/n]?"
read ans
if [ $ans = y -o $ans = Y -o $ans = yes -o $ans = Yes -o $ans = YES ]
then
echo "'yes'"
cd $TRASH_DIR && $EMPTY_TRASH
fi
if [ $ans = n -o $ans = N -o $ans = no -o $ans = No -o $ans = NO ]
then
echo "'no'"
fi
return $TRUE
}
#-----------------------------------------------------------------------
start_help(){
echo "HELP COMMANDS-----------------------------"
echo "htest www open a homepage "
echo "htest trash empty trash "
return $TRUE
} #end Help
#-----------------------------------------------#
homepage=""
return $TRUE
} #end cpdebtemp
# -Case start
# if no command line arg given
# set val to Unknown
if [ -z $1 ]
then
val="*** Unknown ***"
elif [ -n $1 ]
then
# otherwise make first arg as val
val=$1
fi
# use case statement to make decision for rental
case $val in
"trash") start_trash ;;
"help") start_help ;;
"www") firefox $homepage ;;
*) echo "Sorry, I can not get a $val for you!";;
esac
# Case stop