Bash basics: Difference between revisions
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Bash certainly has its set of snafus. | Bash certainly has its set of snafus. | ||
=== store commands in variables === | |||
<pre># NOTE don't put spaces around equals sign! | <pre># NOTE don't put spaces around equals sign! | ||
# NOTE don't use ampersands within command strings, they won't work | # NOTE don't use ampersands within command strings, they won't work | ||
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$mycmd1 && $mycmd2 && $mycmd3 | $mycmd1 && $mycmd2 && $mycmd3 | ||
</pre> | </pre> | ||
=== capture output === | |||
<pre>myout=`program1 param`;</pre> | <pre>myout=`program1 param`;</pre> | ||
* Note the difference a single quote makes to output... | * Note the difference a single quote makes to output... | ||
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abc def | abc def | ||
</pre> | </pre> | ||
=== check for an error === | |||
<pre>mkdir "$d2" | <pre>mkdir "$d2" | ||
if [ $? -gt 0 ]; then | if [ $? -gt 0 ]; then | ||
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fi | fi | ||
</pre> | </pre> | ||
=== read input from user === | |||
<pre>echo "Create the subdirectory? [$d2]" | <pre>echo "Create the subdirectory? [$d2]" | ||
if read answer; then | if read answer; then | ||
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fi</pre> | fi</pre> | ||
[http://www.panix.com/~elflord/unix/grep.html grep | === [http://www.panix.com/~elflord/unix/grep.html powerful grep options] === | ||
Revision as of 13:43, 7 July 2017
Bash certainly has its set of snafus.
store commands in variables
# NOTE don't put spaces around equals sign! # NOTE don't use ampersands within command strings, they won't work # use a blank command if needed, that's fine mycmd1="command param param" mycmd2="cmd2 param" if [ -e /myspecialplace ] mycmd2="" fi mycmd3="cmd3 param" $mycmd1 && $mycmd2 && $mycmd3
capture output
myout=`program1 param`;
- Note the difference a single quote makes to output...
$ eval echo "abc def" abc def $ eval 'echo "abc def"' abc def
check for an error
mkdir "$d2" if [ $? -gt 0 ]; then echo "mkdir error, try that again..." exit 3 fi
read input from user
echo "Create the subdirectory? [$d2]"
if read answer; then
if [ ${answer} = "y" ] || [ ${answer} = "yes" ]; then
{whatever}
else
{whatever}
fi
fi