hello, i have a problem with my script
#!/bin/bash
linenum=$(grep -n -w somedata /usr/local/xx/xxx.txt |cut -f1 -d:);
if [ $linenum > 0 ]
then
linestart=$((linenum-1));
linesend=$((linenum+3));
sed -i "$linestart,$linesend d" /usr/local/xx/xxx.txt;
fi
this script works fine from terminal but from php (exec_shell) i have this message ('permission denied'), when i remove 'if then fi' the script work fine, 
Correct is
if [ $linenum -gt 0 ]
The > 0 is a redirection to a file "0"! Bash handles it differently unless called with --posix.
thank you sir 
Not even with --posix . It is not part of the POSIX specification.
Even so, most shells do support string comparison when the > or < is escaped, through their shell builtin
[ "$string1" \> "$string2 ]
This is not supported by the external test command, however, so in Bourne shell this will not work
--
But what is required here is a numerical comparison which requires the -gt operator, as stated before..