--- name: "exect" section: "3" platform: "linux" package: "manpages" version: "1.15-4" release: "Debian 1.3 (Bo)" platforms: ["linux", "freebsd"] url: "https://new.carta.tech/exec/3" --- # exect(3) execute a file Part of [exec(3)](/exec/3.md). ## NAME execl, execlp, execle, exect, execv, execvp - execute a file ## SYNOPSIS **#include \** **extern char \*\*environ;** **int execl( const char \****path***, const char \****arg***, ...);**\ **int execlp( const char \****file***, const char \****arg***, ...);**\ **int execle( const char \****path***, const char \****arg* **, ..., char \* const** *envp***\[\]);**\ **int exect( const char \****path***, char \*const** *argv***\[\]);**\ **int execv( const char \****path***, char \*const** *argv***\[\]);**\ **int execvp( const char \****file***, char \*const** *argv***\[\]);** ## DESCRIPTION The **exec** family of functions replaces the current process image with a new process image. The functions described in this manual page are front-ends for the function [**execve**(2)](/execve/2.md). (See the manual page for **execve** for detailed information about the replacement of the current process.) The initial argument for these functions is the pathname of a file which is to be executed. The *const char \*arg* and subsequent ellipses in the **execl**, **execlp**, and **execle** functions can be thought of as *arg0*, *arg1*, ..., *argn*. Together they describe a list of one or more pointers to null-terminated strings that represent the argument list available to the executed program. The first argument, by convention, should point to the file name associated with the file being executed. The list of arguments *must* be terminated by a **NULL** pointer. The **exect**, **execv**, and **execvp** functions provide an array of pointers to null-terminated strings that represent the argument list available to the new program. The first argument, by convention, should point to the file name associated with the file begin executed. The array of pointers *must* be terminated by a **NULL** pointer. The **execle** and **exect** functions also specify the environment of the executed process by following the **NULL** pointer that terminates the list of arguments in the parameter list or the pointer to the argv array with an additional parameter. This additional parameter is an array of pointers to null-terminated strings and *must* be terminated by a **NULL** pointer. The other functions take the environment for the new process image from the external variable *environ* in the current process. Some of these functions have special semantics. The functions **execlp** and **execvp** will duplicate the actions of the shell in searching for an executable file if the specified file name does not contain a slash (/) character. The search path is the path specified in the environment by the **PATH** variable. If this variable isn't specified, the default path \`\`/bin:/usr/bin:'' is used (is this true for Linux?). In addition, certain errors are treated specially. If permission is denied for a file (the attempted **execve** returned **EACCES**), these functions will continue searching the rest of the search path. If no other file is found, however, they will return with the global variable *errno* set to **EACCES**. If the header of a file isn't recognized (the attempted **execve** returned **ENOEXEC**), these functions will execute the shell with the path of the file as its first argument. (If this attempt fails, no further searching is done.) If the file is currently busy (the attempted **execve** returned **ETXTBUSY**), these functions will sleep for several seconds, periodically re-attempting to execute the file. (Is this true for Linux?) The function **exect** executes a file with the program tracing facilities enabled (see [**ptrace**(2)](/ptrace/2.md)). ## RETURN VALUES If any of the **exec** functions returns, an error will have occurred. The return value is -1, and the global variable *errno* will be set to indicate the error. ## FILES */bin/sh* ## ERRORS **Execl**, **execle**, **execlp** and **execvp** may fail and set *errno* for any of the errors specified for the library functions [**execve**(2)](/execve/2.md) and [**malloc**(3)](/malloc/3.md). **Exect** and **execv** may fail and set *errno* for any of the errors specified for the library function [**execve**(2)](/execve/2.md). ## SEE ALSO [**sh**(1)](/sh/1.md), [**execve**(2)](/execve/2.md), [**fork**(2)](/fork/2.md), **trace**(2), [**environ**(5)](/environ/5.md), [**ptrace**(2)](/ptrace/2.md) ## COMPATIBILITY Historically, the default path for the **execlp** and **execvp** functions was \`\`:/bin:/usr/bin''. This was changed to place the current directory last to enhance system security. The behavior of **execlp** and **execvp** when errors occur while attempting to execute the file is historic practice, but has not traditionally been documented and is not specified by the POSIX standard. Traditionally, the functions **execlp** and **execvp** ignored all errors except for the ones described above and **ENOMEM** and **E2BIG**, upon which they returned. They now return if any error other than the ones described above occurs. ## STANDARDS **Execl**, **execv**, **execle**, **execlp** and **execvp** conform to IEEE Std1003.1-88 (\`\`POSIX.1'').