Sponsored Content
Top Forums Shell Programming and Scripting How to check for Input Redirection in my script? Post 302408499 by bakunin on Monday 29th of March 2010 04:40:42 PM
Old 03-29-2010
You could accept a specific option like "-f /path/to/inputfile" and act according to this option being set or not. Below is a sketch of the logic for better understanding. Use "getopts" instead of my construction for a production-grade script:

Code:
#! /bin/ksh

typeset inFile=""

while [ -n "$1" ] ; do
     case $1 in
          -f)
               shift
               inFile="$1"
               shift
               ;;

          -x)
               # some other option
               shift
               ;;

          *)
               print - "Error: unknown option"
               exit 1
               ;;

     esac
done

# if $inFile is empty the user has not specified any input file
if [ -n "$inFile" ] ; then
     # interactive operation goes here
else
     # batch operation goes here
fi

exit 0

Now "script -f /some/file" would lead to batch operation whereas "script" would lead to interactive operation.

I hope this helps.

bakunin
 

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

Input Redirection

Hi everybody, first of all i am a new member in UNIX.com and this is my first post. I am impressed with the amount of information a person can ever have in this forum, it is really great having something similiar; anyways let me tell you about the problem I am having, hope you will answer me.... (6 Replies)
Discussion started by: majeed73
6 Replies

2. Shell Programming and Scripting

input redirection question

Hi, in my script I need to execute the following command: query $id 456 432 but it waits for a RETURN character from keyboard and therefore, it fails. I tried something like: query $id 456 432 << '\n' but, i'ts clear it is not correct. Is there any way to do this? Thxs. (0 Replies)
Discussion started by: luistid
0 Replies

3. Shell Programming and Scripting

Asking about shell script input output redirection

Hi, Can anyone please tell me what these lines do? ls >& outfile ls outfile 2>&1 Thanks. (1 Reply)
Discussion started by: trivektor
1 Replies

4. Shell Programming and Scripting

permanent redirection of standard input

while running a user inter-active program how can we get the commands from a file instead of the user? is there anyway to permanently redirect content of a file to standard input? (6 Replies)
Discussion started by: gfhgfnhhn
6 Replies

5. Shell Programming and Scripting

Input redirection and for loop

Hello, I need help with a bash script that I try to improve. I could not find answer so far, maybe because I'm not to familiar with the terminology so feel free to correct my language. I have a script that looks like: NODES="node_a node_b node_c" for NODE in $NODES do ... (4 Replies)
Discussion started by: pn8830
4 Replies

6. Shell Programming and Scripting

Read input and output redirection filename within a script

Hello everyone, My requirement is that within a script I need to construct the command line exactly that it was invoked with. For example : sh a.sh arg1 arg2 arg3 < input.txt > output.txt Now within a.sh, I construct a file which has these contents " sh a.sh arg1 arg2 arg3 < input.txt >... (8 Replies)
Discussion started by: hedonist12
8 Replies

7. Shell Programming and Scripting

How to check the user input to be valid using shell script?

How to check the user input to be valid using shell script? The valid input is in the format like as follows. 1. It can only have r,w,x or a hyphen and nothing else. 2. ensure the r, w, x are in the correct order. for example: rwxr-xr-x is a valid format. Thanks (5 Replies)
Discussion started by: hyeewang
5 Replies

8. UNIX for Dummies Questions & Answers

When do I use input redirection?

Can someone please explain when input redirection is necessary? For example, "cat filename" and "cat< filename" produce the same result. I was told that if I need to bunzip a file that I should type "bunzip2<filename.bz2." However, if I omit the "<" I still get the same result. Can someone... (4 Replies)
Discussion started by: PTcharger
4 Replies

9. Shell Programming and Scripting

Input redirection script

Hi, #!/bin/bash while ; do rm -f /tmp/pipe mkfifo /tmp/pipe ./yuv4mpeg_to_v4l2 < /tmp/pipe & mplayer tom_and_jerry.mp4 -vf scale=480:360 -vo yuv4mpeg:file=/tmp/pipe sleep 65; done When I run this - after mplayer finishes playing video it says - Exiting... (End of... (2 Replies)
Discussion started by: ashokvpp
2 Replies

10. Shell Programming and Scripting

Input redirection within bash script

Hi, when I try to redirect input and the command is described as a string within an array redirection does not work. why? #!/bin/bash dir=("tail < ./hello.txt") tail < ./hello.txt #works ${dir} #does not work (2 Replies)
Discussion started by: heinzel
2 Replies
getoptcvt(1)							   User Commands						      getoptcvt(1)

NAME
getoptcvt - convert to getopts to parse command options SYNOPSIS
/usr/lib/getoptcvt [-b] filename /usr/lib/getoptcvt DESCRIPTION
/usr/lib/getoptcvt reads the shell script in filename, converts it to use getopts instead of getopt, and writes the results on the standard output. getopts is a built-in Bourne shell command used to parse positional parameters and to check for valid options. See sh(1). It supports all applicable rules of the command syntax standard (see Rules 3-10, intro(1)). It should be used in place of the getopt command. (See the NOTES section below.) The syntax for the shell's built-in getopts command is: getopts optstring name [ argument...] optstring must contain the option letters the command using getopts will recognize; if a letter is followed by a colon (:), the option is expected to have an argument, or group of arguments, which must be separated from it by white space. Each time it is invoked, getopts places the next option in the shell variable name and the index of the next argument to be processed in the shell variable OPTIND. Whenever the shell or a shell script is invoked, OPTIND is initialized to 1. When an option requires an option-argument, getopts places it in the shell variable OPTARG. If an illegal option is encountered, ? will be placed in name. When the end of options is encountered, getopts exits with a non-zero exit status. The special option -- may be used to delimit the end of the options. By default, getopts parses the positional parameters. If extra arguments (argument ...) are given on the getopts command line, getopts parses them instead. So that all new commands will adhere to the command syntax standard described in intro(1), they should use getopts or getopt to parse posi- tional parameters and check for options that are valid for that command (see the NOTES section below). OPTIONS
The following option is supported: -b Makes the converted script portable to earlier releases of the UNIX system. /usr/lib/getoptcvt modifies the shell script in file- name so that when the resulting shell script is executed, it determines at run time whether to invoke getopts or getopt. EXAMPLES
Example 1: Processing the arguments for a command The following fragment of a shell program shows how one might process the arguments for a command that can take the options -a or -b, as well as the option -o, which requires an option-argument: while getopts abo: c do case $c in a | b) FLAG=$c;; o) OARG=$OPTARG;; ?) echo $USAGE exit 2;; esac done shift `expr $OPTIND - 1` Example 2: Equivalent code expressions This code accepts any of the following as equivalent: cmd -a -b -o "xxx z yy" filename cmd -a -b -o "xxx z yy" -filename cmd -ab -o xxx,z,yy filename cmd -ab -o "xxx z yy" filename cmd -o xxx,z,yy b a filename ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables that affect the execution of getopts: LC_CTYPE, LC_MESSAGES, and NLSPATH. OPTIND This variable is used by getoptcvt as the index of the next argument to be processed. OPTARG This variable is used by getoptcvt to store the argument if an option is using arguments. EXIT STATUS
The following exit values are returned: 0 An option, specified or unspecified by optstring, was found. >0 The end of options was encountered or an error occurred. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ |CSI |enabled | +-----------------------------+-----------------------------+ SEE ALSO
intro(1), getopts(1), sh(1), shell_builtins(1), getopt(3C), attributes(5) DIAGNOSTICS
getopts prints an error message on the standard error when it encounters an option letter not included in optstring. NOTES
Although the following command syntax rule (see intro(1)) relaxations are permitted under the current implementation, they should not be used because they may not be supported in future releases of the system. As in the EXAMPLES section above, -a and -b are options, and the option -o requires an option-argument. The following example violates Rule 5: options with option-arguments must not be grouped with other options: example% cmd -aboxxx filename The following example violates Rule 6: there must be white space after an option that takes an option-argument: example% cmd -ab oxxx filename Changing the value of the shell variable OPTIND or parsing different sets of arguments may lead to unexpected results. SunOS 5.10 7 Jan 2000 getoptcvt(1)
All times are GMT -4. The time now is 08:35 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy