How can I pass a file argument to my bash script using a Terminal command in Linux?
LinuxBashShellCommand LineTerminalLinux Problem Overview
So my question is how can I pass a file argument to my bash script using a Terminal command in Linux?
At the moment I'm trying to make a program in bash that can take a file argument from the Terminal and use it as a variable in my program. For example I run
myprogram --file=/path/to/file
in Terminal.
My Program
#!/bin/bash
File=(the path from the argument)
externalprogram $File (other parameters)
How can I achieve this with my program?
Linux Solutions
Solution 1 - Linux
It'll be easier (and more "proper", see below) if you just run your script as
myprogram /path/to/file
Then you can access the path within the script as $1
(for argument #1, similarly $2
is argument #2, etc.)
file="$1"
externalprogram "$file" [other parameters]
Or just
externalprogram "$1" [otherparameters]
If you want to extract the path from something like --file=/path/to/file
, that's usually done with the getopts
shell function. But that's more complicated than just referencing $1
, and besides, switches like --file=
are intended to be optional. I'm guessing your script requires a file name to be provided, so it doesn't make sense to pass it in an option.
Solution 2 - Linux
you can use getopt to handle parameters in your bash script. there are not many explanations for getopt out there. here is an example:
#!/bin/sh
OPTIONS=$(getopt -o hf:gb -l help,file:,foo,bar -- "$@")
if [ $? -ne 0 ]; then
echo "getopt error"
exit 1
fi
eval set -- $OPTIONS
while true; do
case "$1" in
-h|--help) HELP=1 ;;
-f|--file) FILE="$2" ; shift ;;
-g|--foo) FOO=1 ;;
-b|--bar) BAR=1 ;;
--) shift ; break ;;
*) echo "unknown option: $1" ; exit 1 ;;
esac
shift
done
if [ $# -ne 0 ]; then
echo "unknown option(s): $@"
exit 1
fi
echo "help: $HELP"
echo "file: $FILE"
echo "foo: $FOO"
echo "bar: $BAR"
see also:
- the "canonical" example: http://software.frodo.looijaard.name/getopt/docs/getopt-parse.bash
- a blog post: http://www.missiondata.com/blog/system-administration/17/17/
man getopt
links dead. here from internet archive:
Solution 3 - Linux
Bash supports a concept called "Positional Parameters". These positional parameters represent arguments that are specified on the command line when a Bash script is invoked.
Positional parameters are referred to by the names $0
, $1
, $2
... and so on. $0
is the name of the script itself, $1
is the first argument to the script, $2
the second, etc. $*
represents all of the positional parameters, except for $0
(i.e. starting with $1
).
An example:
#!/bin/bash
FILE="$1"
externalprogram "$FILE" <other-parameters>
Solution 4 - Linux
Assuming you do as David Zaslavsky suggests, so that the first argument simply is the program to run (no option-parsing required), you're dealing with the question of how to pass arguments 2 and on to your external program. Here's a convenient way:
#!/bin/bash
ext_program="$1"
shift
"$ext_program" "$@"
The shift
will remove the first argument, renaming the rest ($2
becomes $1, and so on).
$@` refers to the arguments, as an array of words (it must be quoted!).
If you must have your --file
syntax (for example, if there's a default program to run, so the user doesn't necessarily have to supply one), just replace ext_program="$1"
with whatever parsing of $1
you need to do, perhaps using getopt or getopts.
If you want to roll your own, for just the one specific case, you could do something like this:
if [ "$#" -gt 0 -a "${1:0:6}" == "--file" ]; then
ext_program="${1:7}"
else
ext_program="default program"
fi