The Dash shell, a POSIX-compliant derivative of the Almquist shell used as /bin/sh in Debian, Ubuntu and other Linux distributions

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958 views

In a script, check if standard input comes from a file or pipe

I know this has been poorly covered previously, but those answers either lack explanation or don't apply. Basically at some point my scripts needs check if a file is specified, if it was it will be ...
0
votes
2answers
4k views

Why does this incrementing for loop return a bad variable?

I'm trying to call this shell script from within the CLI of GRASS GIS: for (( day=5; day<367; day+5 )); do # commands that I've tested without a loop. done exit 0 returns Syntax error: Bad ...
0
votes
1answer
2k views

How to pkill from a script?

How can I write a script that basically just runs pkill -HUP inetd? I want to restart inetd via a script so I can schedule it to run at a particular time. I tried to write it myself, but I'm getting a ...
11
votes
2answers
889 views

What is the difference between : and true?

In bash: $ type : : is a shell builtin $ type true true is a shell builtin Looks like they are the same, but they don't give the same system trace: $ strace : strace: :: command not found $ strace ...
4
votes
2answers
2k views

Getopts option processing, Is it possible to add a non hyphenated [FILE]?

I'm using getopts for all of my scripts that require advanced option parsing, and It's worked great with dash. I'm familiar with the standard basic getopts usage, consisting of [-x] and [-x OPTION]. ...
5
votes
2answers
556 views

Can I trace a dash script without modifying its source code?

I would like to trace a shell script for debugging purposes without having to modify its source code (e.g. change the shebang or insert a set -x at the beginning). It is a dpkg postinst script, so not ...
0
votes
1answer
970 views

POSIX and Bash, sh shorthand, for compound if statement

I prefer to do my sh commands in shorthand, And I prefer to be in POSIX. Truthfully, if the script can run on Dash, that is good enough. Which means using the test command [, not the extended [[. I ...
1
vote
1answer
176 views

How does this bash function work?

I'm looking at this short example, and I don't see how this function works: function EXT_COLOR () { echo -ne "\[\033[38;5;$1m\]"; } AFAIK -ne stands for not equal. What are we comparing here? I ...
5
votes
2answers
1k views

Will I be able to build LFS using dash and mawk?

I decided that I want to learn more about Linux and try building LFS. I'm using Ubuntu 11.04 as host system and Ubuntu uses dash and mawk by default. I've changed mawk to gawk, but considering that ...
2
votes
4answers
3k views

Shell script error message

I am trying to learn shell scripting by reading linuxcommand.org. For some reason I keep getting the error "Not Found", even though it runs all the commands. The error codes I get are: ...
5
votes
2answers
1k views

dash compatibility to bash

Wikipedia says that dash executes faster than bash. My question is, if I set /bin/sh to dash, will all scripts that use /bin/sh in their shebang line that was intended for bash work under dash?