Taking input in a script and making sure there's only one parameter
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I'm currently working on an assignment where I have a script that is basically just getting to learn using grep with different regex's.
I have the script written except for the first part where I am asked to take a file as input and then the script runs based on that file.
I have the prompt for input, the read command after, the grep commands. Everything works fine, I just need to implement an if statement I believe that would run the script if it only has 1 parameter given.
- The assignment says that the script should only run if 1 and only 1 parameter is given otherwise it should display an error message.
Thanks,
bash scripting
asked Mar 16 at 19:33
GrappleGrapple
82
add a comment |
I'm currently working on an assignment where I have a script that is basically just getting to learn using grep with different regex's.
I have the script written except for the first part where I am asked to take a file as input and then the script runs based on that file.
I have the prompt for input, the read command after, the grep commands. Everything works fine, I just need to implement an if statement I believe that would run the script if it only has 1 parameter given.
- The assignment says that the script should only run if 1 and only 1 parameter is given otherwise it should display an error message.
Thanks,
bash scripting
asked Mar 16 at 19:33
GrappleGrapple
82
2
Well, here's how to How to check if there are no parameters provided to a command - see if you can modify it ;)
– steeldriver
Mar 16 at 19:36
add a comment |
I'm currently working on an assignment where I have a script that is basically just getting to learn using grep with different regex's.
I have the script written except for the first part where I am asked to take a file as input and then the script runs based on that file.
I have the prompt for input, the read command after, the grep commands. Everything works fine, I just need to implement an if statement I believe that would run the script if it only has 1 parameter given.
- The assignment says that the script should only run if 1 and only 1 parameter is given otherwise it should display an error message.
Thanks,
bash scripting
asked Mar 16 at 19:33
GrappleGrapple
82
I'm currently working on an assignment where I have a script that is basically just getting to learn using grep with different regex's.
I have the script written except for the first part where I am asked to take a file as input and then the script runs based on that file.
I have the prompt for input, the read command after, the grep commands. Everything works fine, I just need to implement an if statement I believe that would run the script if it only has 1 parameter given.
- The assignment says that the script should only run if 1 and only 1 parameter is given otherwise it should display an error message.
Thanks,
bash scripting
bash scripting
asked Mar 16 at 19:33
GrappleGrapple
82
asked Mar 16 at 19:33
GrappleGrapple
82
asked Mar 16 at 19:33
GrappleGrapple
82
asked Mar 16 at 19:33
GrappleGrapple
82
asked Mar 16 at 19:33
GrappleGrapple
82
82
2
Well, here's how to How to check if there are no parameters provided to a command - see if you can modify it ;)
– steeldriver
Mar 16 at 19:36
add a comment |
2
Well, here's how to How to check if there are no parameters provided to a command - see if you can modify it ;)
– steeldriver
Mar 16 at 19:36
2
2
Well, here's how to How to check if there are no parameters provided to a command - see if you can modify it ;)
– steeldriver
Mar 16 at 19:36
Well, here's how to How to check if there are no parameters provided to a command - see if you can modify it ;)
– steeldriver
Mar 16 at 19:36
add a comment |
1 Answer
1
active
oldest
votes
Within a script $# will expand to the number of positional parameters. We can use that to check if the correct number of options have been passed, and exit right away if not:
#!/bin/sh
if [ "$#" -ne 1 ]; then
printf 'ERROR! You must provide one and only one argument!n' >&2
exit 1
fi
Places you can read about this:
2.5.1 Positional Parameters
The if Conditional Construct
2.7.2 Redirecting Output
answered Mar 16 at 19:44
Jesse_bJesse_b
14.4k33574
add a comment |
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1 Answer
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1 Answer
1
active
oldest
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active
oldest
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active
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votes
Within a script $# will expand to the number of positional parameters. We can use that to check if the correct number of options have been passed, and exit right away if not:
#!/bin/sh
if [ "$#" -ne 1 ]; then
printf 'ERROR! You must provide one and only one argument!n' >&2
exit 1
fi
Places you can read about this:
2.5.1 Positional Parameters
The if Conditional Construct
2.7.2 Redirecting Output
answered Mar 16 at 19:44
Jesse_bJesse_b
14.4k33574
add a comment |
Within a script $# will expand to the number of positional parameters. We can use that to check if the correct number of options have been passed, and exit right away if not:
#!/bin/sh
if [ "$#" -ne 1 ]; then
printf 'ERROR! You must provide one and only one argument!n' >&2
exit 1
fi
Places you can read about this:
2.5.1 Positional Parameters
The if Conditional Construct
2.7.2 Redirecting Output
answered Mar 16 at 19:44
Jesse_bJesse_b
14.4k33574
add a comment |
Within a script $# will expand to the number of positional parameters. We can use that to check if the correct number of options have been passed, and exit right away if not:
#!/bin/sh
if [ "$#" -ne 1 ]; then
printf 'ERROR! You must provide one and only one argument!n' >&2
exit 1
fi
Places you can read about this:
2.5.1 Positional Parameters
The if Conditional Construct
2.7.2 Redirecting Output
answered Mar 16 at 19:44
Jesse_bJesse_b
14.4k33574
Within a script $# will expand to the number of positional parameters. We can use that to check if the correct number of options have been passed, and exit right away if not:
#!/bin/sh
if [ "$#" -ne 1 ]; then
printf 'ERROR! You must provide one and only one argument!n' >&2
exit 1
fi
Places you can read about this:
2.5.1 Positional Parameters
The if Conditional Construct
2.7.2 Redirecting Output
answered Mar 16 at 19:44
Jesse_bJesse_b
14.4k33574
edited Mar 16 at 21:31
answered Mar 16 at 19:44
Jesse_bJesse_b
14.4k33574
answered Mar 16 at 19:44
Jesse_bJesse_b
14.4k33574
answered Mar 16 at 19:44
Jesse_bJesse_b
14.4k33574
14.4k33574
add a comment |
add a comment |
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2
Well, here's how to How to check if there are no parameters provided to a command - see if you can modify it ;)
– steeldriver
Mar 16 at 19:36