PHP shell exec vs exec

Question

I m struggling to understand the difference between shell exec   and exec       I ve always used exec   to execute server side commands  when would I use shell exec     Is shell exec   just a shorthand for exec     It seems to be the same thing with fewer parameters

User · Answer

shell exec - Execute command via shell and return the complete output as a string  exec - Execute an external program   The difference is that with shell exec you get output as a return value

User · Answer

shell exec returns all of the output stream as a string  exec returns the last line of the output by default  but can provide all output as an array specifed as the second parameter   See   http   php net manual en function shell-exec php http   php net manual en function exec php

User · Answer

Here are the differences  Note the newlines at the end    gt  shell exec  date   string 29   Wed Mar  6 14 18 08 PST 2013 n   gt  exec  date   string 28   Wed Mar  6 14 18 12 PST 2013    gt  shell exec  whoami   string 9   mark n   gt  exec  whoami   string 8   mark    gt  shell exec  ifconfig   string 1244   eth0      Link encap Ethernet  HWaddr 10 bf 44 44 22 33   n          inet addr 192 168 0 90  Bcast 192 168 0 255  Mask 255 255 255 0 n          inet6 addr  fe80  12bf ffff eeee 2222 64 Scope Link n          UP BROADCAST RUNNING MULTICAST  MTU 1500  Metric 1 n          RX packets 16264200 errors 0 dropped 1 overruns 0 frame 0 n          TX packets 7205647 errors 0 dropped 0 overruns 0 carrier 0 n          collisions 0 txqueuelen 1000  n          RX bytes 13151177627  13 1 GB   TX bytes 2779457335  2 7 GB  n      gt  exec  ifconfig   string 0       Note that use of the backtick operator is identical to shell exec     Update  I really should explain that last one  Looking at this answer years later even I don t know why that came out blank  Daniel explains it above -- it s because exec only returns the last line  and ifconfig s last line happens to be blank

User · Answer

A couple of distinctions that weren t touched on here    With exec    you can pass an optional param variable which will receive an array of output lines   In some cases this might save time  especially if the output of the commands is already tabular    Compare   exec  ls    out   var dump  out      Look an array   out   shell exec  ls    var dump  out      Look -- a string with newlines in it   Conversely  if the output of the command is xml or json  then having each line as part of an array is not what you want  as you ll need to post-process the input into some other form  so in that case use shell exec   It s also worth pointing out that shell exec is an alias for the backtic operator  for those used to  nix    out    ls   var dump  out     exec also supports an additional parameter that will provide the return code from the executed command   exec  ls    out   status   if  0      status        var dump  out     else       echo  Command failed with status   status       As noted in the shell exec manual page  when you actually require a return code from the command being executed  you have no choice but to use exec

[php] PHP shell_exec() vs exec()

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