Question

I’m writing a script that asks the user for several options and then, via a series of echo statements, creates and writes to a separate script file. That script will also be dependent on at least one command line argument when executed.

Given the original statement

if [ "` echo $1 | egrep ^[[:digit:]]+$`" = "" ]

that determines if the first argument ($1) is an integer, how can I include that in the echo statement to be written to the new file while maintaining the command line argument access?

I tried to escape the double quotes and dollar signs like

echo "if [ \"` echo \$1 | egrep ^[[:digit:]]+\$`\" = \"\" ]" >> generatePanos

but that just resulted in

if [ "" = "" ]

However, echo "\$1" results in $1 being printed in the file.

Answer 1

I’m not entirely certain what you mean, but here are two things you can try:

If you’re trying to print the entire line as-is (including the $1), use single-quotes to tell echo to not interpret anything:

$ echo 'if [ "` echo $1 | egrep ^[[:digit:]]+$`" = "" ]'
if [ "` echo $1 | egrep ^[[:digit:]]+$`" = "" ]

If you’re trying to print the entire line but substitute in the current value for $1:

$ echo "if [ \"\` echo $1 | egrep ^[[:digit:]]+\$\`\" = \"\" ]"
if [ "` echo <<some value>> | egrep ^[[:digit:]]+$`" = "" ]

If you’re trying to substitute the entire portion of the command that’s in backticks (evaluated using the current value of $1), it’s probably best to use an intermediate variable:

temp=$(echo $1 | egrep ^[[:digit:]]+$)
echo "if [ \"$temp\" = \"\" ]"